Activation of trpv4 ion channel by physical stimuli and critical role for trpv4 in organ-specific inflammation and itch

ABSTRACT

Provided are methods of treating and/or preventing dermatological disorders. Provided are methods of reducing skin inflammation, reducing pain, and/or reducing itch in a subject in need thereof. The methods may include administering to the subject an effective amount of a TRPV4 inhibitor. Further provided are compositions including a TRPV4 inhibitor compound in combination with a carrier, vehicle, or diluent that is suitable for topical application. Further provided is a transgenic mouse whose genome includes deletions of the Trpv4 gene in keratinocytes of the epidermis, wherein said transgenic mouse is a knockout for the Trpv4 gene in keratinocytes of the epidermis following keratinocyte-specific activation and expression of a site-specific recombination enzyme.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application No. 61/668,842, filed Jul. 6, 2012, U.S. Provisional Patent Application No. 61/675,252, filed Jul. 24, 2012, and U.S. Provisional Patent Application No. 61/698,118, filed Sep. 7, 2012, each of which is incorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

This invention was made with government support under grant numbers DE018549 and DE018529S1 awarded by the National Institutes of Health/National Institute of Dental and Craniofacial Research (NIH/NIDCR), and grant numbers AR059402, AR31737, and AR050452 awarded by the National Institutes of Health/National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIH/NIAMS). The government has certain rights in the invention.

FIELD

This disclosure relates to methods and compositions for treating inflammation, pain, itch, cancer, autoimmune diseases, fibrotic diseases, skin pigmentation, and/or other dermatological disorders.

INTRODUCTION

The skin is the largest organ in many vertebrates, including humans. It provides barrier protection against the potentially harmful external environment. The skin also represents the site of first interaction of the ambient environment to immunologically competent and sentient structures of the organism. Cells endowed with sensory transduction capacity for warmth, cold, mechanical cues, pain, and itch are sensory neurons in the dorsal root and trigeminal ganglia with their peripheral axons directly interfacing with skin.

TRPV4 is a multimodally-activated non-selective cation channel permeable to calcium (i.e., Ca++). In epidermal keratinocytes of mammalian skin, the TRPV4 ion channel is expressed robustly. However, TRPV4 is also expressed in skin-innervating sensory neurons. In Trpv4−/− mice, an epidermal phenotype of impaired barrier function between epidermis and dermis has been shown. In regards to pain signaling, Trpv4 has been found critical for physiological withdrawal responses to noxious osmotic and mechanical, but not thermal cues, and has also been found relevant for inflammation or nerve-damage-induced sensitization of nociception. While it is understood that TRPV4 is expressed in epidermal keratinocytes and skin-innervating sensory neurons, an in-vivo role of TRPV4 in pathological pain evoked by UVB exposure has not been demonstrated. Moreover, a direct role of TRPV4 in itch transmission has not been demonstrated as of yet.

SUMMARY

In an aspect, the disclosure relates to methods of treating and/or preventing a dermatological disorder in a subject in need thereof. The methods may include administering to the subject an effective amount of a TRPV4 inhibitor. The dermatological disorder may be selected from inflammation, pain, itch, cancer, autoimmune diseases, fibrotic diseases, skin pigmentation, and/or other dermatological disorders. The TRPV4 inhibitor may include a compound according to Formula I:

wherein A, B, and C are independently selected from the group consisting of aromatic, heteroaromatic, cycloalkenyl, and heterocycloalkenyl groups; D is C₁-C₃ alkylene; E is a bond, or C₁-C₂ alkylene; and R is selected from the group consisting of hydrogen, hydroxyl, amino, alkyl, alkenyl, heteroalkyl, aromatic ring, or heteroaromatic ring. The TRPV4 inhibitor may include a compound selected from the following:

In an aspect, the disclosure relates to methods of reducing skin inflammation in a subject in need thereof. The methods may include administering to the subject an effective amount of a TRPV4 inhibitor. The skin inflammation may be related to UVB exposure. The skin inflammation may be associated with a dermatological disorder selected from sunburn, rosacea, Xeroderma pigmentosum, non-melanoma skin cancer, and photoaging, or with a disorder selected from non-UV skin burn, disturbed wound healing, and pain of bone fractures. The method may further include reducing pain in the subject. The TRPV4 inhibitor may include a compound according to Formula I:

wherein A, B, and C are independently selected from the group consisting of aromatic, heteroaromatic, cycloalkenyl, and heterocycloalkenyl groups; D is C₁-C₃ alkylene; E is a bond, or C₁-C₂ alkylene; and R is selected from the group consisting of hydrogen, hydroxyl, amino, alkyl, alkenyl, heteroalkyl, aromatic ring, or heteroaromatic ring. The TRPV4 inhibitor may include a compound selected from the following:

In a further aspect, the disclosure relates to methods of pain management. The methods may include administering to at least a portion of the skin of a subject in need thereof an effective amount of a TRPV4 inhibitor. The pain may be associated with a dermatological disorder selected from sunburn, rosacea, Xeroderma pigmentosum, non-melanoma skin cancer, and photoaging, or with a disorder selected from non-UV skin burn, disturbed wound healing, and pain of bone fractures. The method may further include reducing pain in the subject. The TRPV4 inhibitor may include a compound according to Formula I:

wherein A, B, and C are independently selected from the group consisting of aromatic, heteroaromatic, cycloalkenyl, and heterocycloalkenyl groups; D is C₁-C₃ alkylene; E is a bond, or C₁-C₂ alkylene; and R is selected from the group consisting of hydrogen, hydroxyl, amino, alkyl, alkenyl, heteroalkyl, aromatic ring, or heteroaromatic ring. The TRPV4 inhibitor may include a compound selected from the following:

Another aspect of the disclosure provides methods of reducing itch in a subject in need thereof. The methods may include administering to the subject an effective amount of a TRPV4 inhibitor.

In a further aspect, the disclosure relates to compositions including a TRPV4 inhibitor compound in combination with a carrier, vehicle, or diluent that is suitable for topical application.

In a further aspect, the disclosure relates to topical formulations including a TRPV4 inhibitor, wherein the TRPV4 inhibitor includes a compound according to the following formula:

wherein A, B, and C are independently selected from the group consisting of aromatic, heteroaromatic, cycloalkenyl, and heterocycloalkenyl groups; D is C₁-C₃ alkylene; E is a bond, or C₁-C₂ alkylene; and R is selected from the group consisting of hydrogen, hydroxyl, amino, alkyl, alkenyl, heteroalkyl, aromatic ring, or heteroaromatic ring. The TRPV4 inhibitor may include a compound selected from the following:

In a further aspect, the disclosure relates to novel TRPV4 inhibitors. The TRPV4 inhibitor may be a compound selected from the following:

In a further aspect, the disclosure relates to a transgenic mouse whose genome includes deletions of the Trpv4 gene in keratinocytes of the epidermis, wherein said transgenic mouse is a knockout for the Trpv4 gene in keratinocytes of the epidermis following keratinocyte-specific activation and expression of a site-specific recombination enzyme. A Keratin-14 promoter may drive expression of the site-specific recombination enzyme, wherein the site-specific recombination enzyme is fused to a mutated estrogen receptor, and wherein an anti-estrogen has increased affinity to the mutated estrogen receptor relative to wild-type estrogen such that addition of the anti-estrogen to the transgenic mouse drives the site-specific recombination enzyme to the nucleus and results in knockdown of expression of the Trpv4 gene. The site-specific recombination enzyme may be CRE recombinase. Deletion of the Trpv4 gene may be specifically and conditionally induced in keratinocytes of the epidermis. The keratinocyte-specific deletion of the Trpv4 gene may be induced by applying an anti-estrogen. The anti-estrogen may include tamoxifen. The transgenic mouse may exhibit reduced expression relative to a control of at least one of IL6, ET1, caspase1, IL1β, and CXCL5, or a combination thereof, in response to UVB exposure.

In another aspect, the disclosure relates to assays including a transgenic mouse as described herein.

In a further aspect, the disclosure relates to methods for identifying a selective inhibitor of TRPV4. The methods may include (a) contacting a mouse with a test compound; (b) determining a biological activity of TRPV4 after contacting with the test compound; and (c) determining a control level of biological activity of TRPV4 in the absence of the test compound; (d) comparing the biological activity of TRPV4 from step (b) with the biological activity of TRPV4 from a model of TRPV4 deletion, wherein the model of TRPV4 deletion includes the transgenic mouse as disclosed herein or a pan-null Trpv4−/− mouse; and (e) identifying the test compound as a selective inhibitor of TRPV4 when at least one of (i) the TRPV4 biological activity is lower in the presence of the test compound than the TRPV4 biological activity in the absence of the test compound; (ii) the TRPV4 biological activity in the presence of the test compound is about the same as, or lower than, the TRPV4 biological activity in the model of TRPV4 deletion; or (iii) any combination of (i) and (ii).

The disclosure provides for other aspects and embodiments that will be apparent in light of the following detailed description and accompanying Figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: Keratinocyte-specific and inducible Trpv4 null mouse and its UVB response. (A) Gene-targeting of Trpv4 and genetic manipulation underlying generation of keratinocyte-specific and inducible Trpv4 knockout mice. Shown are sequential steps of mouse Trpv4 targeting, starting with flanking Trvp4 exon13 with loxP elements and insertion of a selection cassette, flanked by frt sites, in mouse embryonic stem cells. After generation of chimeric mice and stable transmission of the engineered mutation, the selection cassette was removed by breeding to FLPe mice. Resulting mice were homozygosed and crossed with K14-CRE-ER^(tam) mice, which then permitted keratinocyte-specific and inducible Trpv4 knockout/knockdown. (B) DNA genotyping. Shown are PCR products of WT, heterozygote and homozygous Trpv4^(lox/lox) mice. Note that the PCR products needed to be digested with PacI, and that all mice were pre-screened to be CRE+ by another genotyping PCR. (C) Co-labeling of mouse skin for keratin-1 and keratin-14 indicate the established pattern for vehicle-induced control mice (upper panel), and a similar pattern for specific TRPV4 knockdown in keratinocytes (lower panel). However, in these animals note a slightly increased expression of K14 in the stratum spinosum, reflecting attenuated TRPV4 expression and thus reduced Ca⁺⁺ influx. K14 is normally down-regulated at the basal-to-suprabasal transition, concomitant with the rise in Ca⁺⁺-signaling and induction of terminal differentiation. (D) TRPV4 protein expression in L5 DRG neurons not different between genotypes. Densitometry of TRPV4 immunohistochemistry in L5 (=foot-pad innervating) DRG neurons (upper panel micrographs), the bar-diagram illustrates the lack of a difference in terms of TRPV4 protein abundance in oil- vs. tam-treated mice, for both base-line and 48 hours after UV exposure, confirming the specificity of TRPV4 knockdown in skin when using K14 as CRE driver. Note the characteristic morphology of decorated cells identifying them as DRG sensory neurons. Note also the different levels of TRPV4 expression in these neurons, as noted previously; n=3 mice/group, ≧50 neurons/mouse. (E) Lack of TRPV4 expression in Merkel cells in foot-pad epidermis. A confocal triple-fluorescent micrograph panel is shown, depicting representative images of immuno-labeled paw-pads from iKO control vs. tamoxifen-induced mice. Note complete knockdown of TRPV4 in this example (red channel). For Merkel cells (green channel), an anti-cytokeratin 8 antibody was used. Note lack of TRPV4 co-labeling in Merkel cells. Blue channel=DAPI. (F) Lack of effect of tamoxifen application in K14-CRE-ER^(tam) mice on UVB behavioral sensitization. Note very similar withdrawal thresholds in (K14-CRE-ER^(tam)×Trpv4^(lox/+)) mice (=Trpv4 heterozygotes in keratinocytes when induced with tamoxifen) for noxious mechanical (upper diagram) and thermal (lower diagram) stimulation; n=7 mice per group. Also note the time-course with peak sensitivity at time-point 48 hours. (G) Size distribution of pERK-expressing L5 DRG neurons in oil-treated iKO mice, exposed to UVB. The bar diagram illustrates size prevalence of small and medium-size sensory neurons that express pERK 48 hours after UVB exposure, note absence of larger neurons (>1200 μm²), n=22 neurons.

FIG. 2: UVB stimulation device and UVB keratinocyte control experiments. (A) UV spectrum emitted by the LEDs, overlapped with the spectrum of quartz (red trace), which is almost fully permeable to UVB, and glass (blue trace), which has a very low UVB permeability. (B) Focusing properties of the ball lens. (C) Focal geometry of the combination of UV-LED and ball lens. (D) Absence of thermal effects of the UV-LEDs; measurement of temperature in the focal point over time. (E) TRPV3 activation experiment. Induction of a Ca++ transient by camphor, which can be blocked effectively by 10 μM IPP, suggesting TRPV3-mediated signaling. (F) TRPV4 selective activator GSK101-related findings. Ca++ transient in 1° MK in response to 5 nM GSK101, which can be completely blocked by 20 μM GSK205, suggesting it is specifically mediated by TRPV4. The GSK101-response can also be eliminated by absence of external Ca++, in keeping with TRPV4 signaling. (G) TRPV4 is sufficient for the UVB-Ca++ response—HEK293T cell heterologous transfection. Directed expression of TRPV4 in HEK293T cells leads to a Ca++-transient in response to UVB radiation, which is greatly reduced in control-transfected cells. Preexposure to 20 μM GSK205 virtually eliminates the Ca++-signal in TRPV4-transfected cells, and eliminates the moderate signal of control-transfected cells.

FIG. 3: Keratinocyte-specific ablation of Trpv4 leads to alterations in nocifensive behavior in response to UVB. (A) Epidermal TRPV4 expression and its loss upon keratinocyte-specific ablation of Trpv4 in tam-induced iKO mice. (i) TRPV4 immunofluorescence. Note TRPV4 in epidermis of vehicle (oil) treated control, but not tam-induced iKO mice. Bar=10 μm. (ii) Western blot of epidermal lysates from paw-pad skin. Note knockdown and more complete loss of TRPV4 following induced Trpv4-ablation (β-actin used for normalization). (iii) qRT-PCR for Trpv4 mRNA from paw-pad skin is shown, indicating significant Trpv4 knockdown in response to tam-treatment vs. carrier (oil). P<0.0001, t-test. (iv) Immunofluorescence for epidermal lineage markers. In WT skin, basal epidermal marker keratin-14 is downregulated and suprabasal marker keratin-1 is induced upon commitment to terminal differentiation. Upon knockdown of TRPV4, this balance appears perturbed, with some spinous layer cells showing co-labeling. Bar=10 μm. (B) Nocifensive behavior in response to UVB exposure. Time-course (in hours) for nocifensive behavior elicited by either a noxious mechanical stimulus (automatic von Frey hair assay, left) or thermally-evoked nocifensive behavior (Hargreaves' assay, right). Note significantly less sensitization in Trpv4^(−/−) and in tam-treated iKO mice, relative to oil-treated (vehicle) iKO and WT mice. n≧10 animals per group; ** p<0.01 ANOVA. (C) Correlation between nocifensive behavior and level of Trpv4 knockdown. n=12 animals are shown for which both parameters were available and Trpv4 mRNA levels <0.45. Note the four vehicle-induced animals (green symbols) vs. their tamoxifen-induced counterparts (red symbols). (D) Loss of epidermal TRPV4 shows no significant effect on nocifensive behaviors caused by formalin injection. Bars depict average cumulative nocifensive behavior within the first 10 minutes (phase I), and 10-45 minutes (phase II) post-injection. n=4 per group. (E) Phosphorylated ERK in L5 DRG neurons. pERK immunofluorescence of L5 DRG sections are shown for oil- and tam-treated iKO animals ±exposure to UVB. Note that only UVB-exposed control mice show pERK expression in the paw-pad-innervating L5 DRG. Quantifications are shown at right. n=3 animals per group, 6 sections per DRG per animal, ** p<0.01 ANOVA.

FIG. 4: Structural and ultrastructural analyses showing that UVB-mediated skin tissue injury depends upon keratinocyte TRPV4, and Immuno-histochemical analysis demonstrates that UVB-mediated activation of keratinocytes and recruitment of macrophages and neutrophils depends upon keratinocyte TRPV4. (A) 1 μm toluidine-blue semi-thin sections. Micrographs show representative findings of skin in response to UVB, sampled 48 hours after UVB exposure. Note that upon UVB stimulation, oil- (TRPV+) but not tam-treated (TRPV−) iKO mice exhibit separations at the epidermal-dermal boundary and robust signs of tissue injury; note granulocytes (Gr, neutrophil). Note also that just beneath the stratum corneum (SC), the upper epidermis shows extensive structural damage which could also be seen in skin of tam-treated iKO mice where Trpv4 knockdown was incomplete, but not in those animals where it was more complete (see Figure S2A). Bars=20 μm. Der=dermis; Epi=epidermis. (B) Ultrastructural findings by EM. Selected areas from 1 μm semithin sections of paw skin were examined by transmission electron microscopy. (A-A′) and (C-C′) show normal epidermal (Epi) structure for both, oil- and tam-treated iKO mice, in the absence of UVB stimulation. (A) and (C) show and intact epidermis. Basal (BL) and spinous (Sp) layers are magnified A′ and C′ displaying a normal organization with no evidence of epidermal damage. (B,B′B″), (D-D′) and (E-E′) show representative findings of skin in response to UVB, sampled 48 h after UVB exposure. (B) Disrupted epidermis in oil treated iKO mice. An area equivalent to the boxed area is magnified in (B′), where granulocyte infiltration of epidermis is evident (Gr) and blistering with detachment of the epidermis from the dermis (double arrows). (B″) Upper part of epidermis in contact with stratum corneum (SC), showing extensive vacuolization and deposits of fibrin inside the vacuoles (asterisks). (D) Tamoxifen treated iKO mice with incomplete knockdown of trvp4 show similar skin phenotype to oil treated iKO mice, with robust signs of tissue damage to basal and spinous layer, fibrin deposits (asterisks) and intercellular spaces (arrowheads in D′). (E) Intact epidermis in iKO with complete knockdown of trvp4, with normal basal and spinous layers in (E′). Der, dermis. Dotted lines indicate the dermo-epidermal boundary. Bars=20 μm for A, B, C and D; 10 μm for B′ and E′ and 2 μm for the other micrographs. (C) IL-6 upregulation in keratinocytes as marker of epidermal activation. IL-6 immunofluorescence reveals a reduced ability of TRPV4-deficient mice to elevate keratinocyte IL-6 expression in response to UVB exposure. Quantifications for protein is shown next to micrograph. Densitometries are for n≧3 mice per group, showing significant upregulation for oil-treated iKO mice, lack thereof for tam-treated. Right-hand bar diagram shows II-6 mRNA quantification and time-course. II-6 mRNA was determined by qPCR after isolation of total RNA from paw-pad epidermis. Note the early and robust increase, albeit with variation, at the 2 hour time-point, in WT control epidermis, in contrast the very moderate increase in Trpv4^(−/−) epidermis. Note also the sustained robust upregulation at 24 hours, again moderately upregulated in Trpv4^(−/−) epidermis. Quantifications are for n=8-12 mice/group. * denotes statistically significant (p=0.011, t-test); scale-bar=20 μm. (D) Recruitment of macrophages in UVB-exposed skin. Note that the numbers of dermal CD68+ macrophages induced by UVB-exposure in control mice is significantly reduced when Trpv4 is ablated in the epidermis. Quantifications are shown at right (n=3 mice/group; * p<0.05 t-test); scale-bar=20 μm. (E) Recruitment of elastase-expressing neutrophils to UVB-exposed skin. Shown are representative immunofluorescence micrographs and respective quantifications. Note a strong increase in abundance of elastase-expressing neutrophils in control mice, and a lack thereof in tam-treated iKO mice. (n=4 mice/group, * p<0.05 t-test); scale-bar=40 μm.

FIG. 5: Histopathology in Trpv4−/− and control mice in response to UVB. (A) Trpv4 knockdown level of samples shown in FIG. 4A-E. This bar diagram shows relative level of knockdown of Trpv4 in comparison with WT, of UVB-exposed skin samples shown in FIG. 4. An adjacent sample of hindpaw skin was RNA-extracted at 48 h post-exposure and subjected to Trpv4 qRT-PCR; pooled WT mRNA values from 10 mice were set as 100%. (B) Light microscopic analyses of 1 μm semithin sections findings from Trpv4−/− and WT control mice. Normal skin is shown in the upper row for both genotypes in the unstimulated state, presence of epidermal and dermal inflammation in WT control vs. absence thereof in Trpv4−/− when exposing the skin to UVB, sampling conducted at 48 hours. Note inflammatory changes similar to those of oil-treated iKO mice, as shown in FIG. 4. (C) Ultrastructural analyses of Trpv4−/− and WT control mice. (A-A′) and (B-B′) WT and Trpv4−/− mice show normal skin morphology with intact epidermis (Epi) in the absence of UVB stimulation. A′ and B′ show higher magnification of basal layer (BL) cells. (C-C′) Damaged epidermis with vacuolization (inset in C) and granulocyte (neutrophil) (granulocyte—Gr) infiltrate (C′). (D-D′) Normal epidermal and dermal ultrastructure in Trpv4−/− mice exposed to UVB. Der—dermis; NT, nerve terminals. Dotted lines indicate the dermo-epidermal boundary. Bars=10 μm for A, B, C, C′ and D and 2 μm for the other micrographs. (D) IL-6 upregulation in epidermal keratinocytes in response to UVB depends on Trpv4; findings from Trpv4−/− and WT control mice. Fluorescent micrographs from Trpv4−/− and WT control skin, unexposed and exposed to UVB are shown. Note strong IL-6 signal in WT, exposed to UVB, and low signal in Trpv4−/− for both non-exposed and UVB-exposed states. Also note IL-6-expressing innervating peripheral nerve endings in the dermis. (E) No difference in mast cell abundance in UVB-photodermatitis in iKO mice. Left-hand micrograph shows mast-cells within sub-epidermal inflammatory tissue, stained with toluidine-blue, in an iKO mouse induced with tamoxifen, right micrograph its counterpart in an oil-treated iKO mouse. Mast-cells are indicated by white arrow-heads. Bar=20 μm. Right-hand bar diagram indicates quantification of mast-cell count per 63× visual field (5 fields per mouse, 3 mice per group).

FIG. 6: Ca++ influx into keratinocytes in response to UVB depends on TRPV4. (A) Custom-built UVB cell illumination apparatus. See also FIG. 2. (B) Fluo-4 Ca++ imaging in 1° MKs. Fluorescent micrographs of 1° MKs after loading with Ca++-sensitive dye, fluo-4, before (upper) and at the end of UVB exposure (lower). Bar=10 μm. C-H UVB-evoked Ca++ signaling profiles. Fluo-4 imaging was used to detect Ca++ transients in 1° MKs following UVB exposure. y-axis indicates the increase in fluorescence, ΔF, normalized for prestimulation signal, F0 (ΔF/F0). The signal shown is that averaged from ≧50 cells. (C) Ca++ signaling is dependent upon UVB, and is strikingly reduced when quartz coverslips are replaced by glass ones, which prevent UVB permeation (see FIG. 2A). Note that this particular Ca++ signal in WT 1° MKs persisted after UVB, as is sometimes observed. (D) UVB-evoked Ca++ signaling is dependent on external [Ca++]. (E) UVB-evoked Ca++ signaling is not seen In Trpv4−/− 1° MKs, revealing the importance of the TRPV4 ion channel. (F) UVB-evoked Ca++ signaling is strongly down-regulated in the presence of TRPV4-selective inhibitor, GSK205 (20 μM). (G) The UVB-evoked Ca++ signal is not inhibited by the TRPV3-selective inhibitor, IPP. For validation of IPP's activity, see FIG. 2E. (H) The UVB-evoked Ca++ signal can be strongly reduced with specific PLC inhibitor, U73122.

FIG. 7: Central role for keratinocyte TRPV4 in UVB-evoked Ca++ signaling and nocifensive behavior—effects of ET1. (A) Effects of ET1 on UVB-evoked Ca++ signaling in 1° MKs. Panel (i) shows averaged Ca++ transients in 1° MK in response to UVB, their augmentation by co-exposure to ET1 peptide, and their significant attenuation by either GSK205, which inhibits TRPV4, or ET-convertase inhibitor CGS35066, which blocks ET1 proteolytic processing. Panel (ii) shows ET-augmented, UVB-induced Ca++ transients as in (i), but in this case, where they are attenuated by selective antagonism of ET(R)-A (BQ123) and ET(R)-B (BQ788). Panel (iii) illustrates the complete elimination of the ET1-augmented Ca++ transients when both subtypes of ET(R) are blocked. (B) 4α-PDD-evoked Ca++ signaling in 1° MKs-ET1-related findings. Left-hand panel shows Ca++ transients (as per fura-2 ratiometric imaging) in response to the selective TRPV4 activator 4α-PDD. A significant increase in the response can be observed by co-application of ET1, and this is partially dependent on ET(R)-A and completely dependent on ET(R)-B. (C) Upregulation of ET1 in mouse paw in response to UVB. Immunohistochemistry reveals a significantly stronger ET1 signal in UVB-exposed skin of oil-vehicle-treated (TRPV4+) rather than tamtreated iKO mice. Quantifications are for n=3 mice/group. *** denotes statistically significant (p<0.001, t-test). (D) Nocifensive behavior in response to ET1 footpad injection depends on epidermal TRPV4. Bar diagram summarizes behavioral findings for Trpv4−/− vs. WT and for oil-treated vs. tam-treated iKO mice. Note that in WT and oil-treated iKO mice, footpad injection of ET1 leads to significant levels of mechanical allodynia. Trpv4−/− and tam-treated iKO mice fail to respond; n≧7 mice/group, ** p<0.01, ANOVA.

FIG. 8: Central role for KC TRPV4 in UVB-evoked Ca⁺⁺ signaling and nocifensive behavior—ET1-related supplementary findings. (A) Augmentation of GSK101-evoked Ca⁺⁺ signaling by ET1. Shown are averaged Ca′ measurements (fura-2) in response to 5 nM GSK101. Note the increase in signal in response to co-exposure to ET1. (B) ET1 secretion by non-stimulated 1° MK depends on TRPV4 and PLC. Shown are relative ET1 concentrations (determined by ELISA, pg/mL; vehicle-treated and WT control normalized to 100) in supernatant of non-stimulated 1° MK. Note the clear dependence on TRPV4, as indicated by a 50% reduction in Trpv4^(−/−) 1*MK. Moreover, there is a significant down-regulation by specific inhibition of TRPV4, which is dose-dependent (two doses of GSK205) and can be mediated by two different compounds (GSK205, RN1734). There is also down-regulation of ET1 secretion by a specific inhibitor of PLC (U73122), and by an ET-convertase inhibitor, CGS35066, which served as a control compound. In addition, PLC-inhibitor robustly affects ET1 secretion in WT and Trpv4^(−/−) 1° MK. (C) ET1 expression by UVB-exposed 1° MK depends on TRPV4 and PLC—immunocytochemistry. Shown is specific ET1 immunolabeling in 1° MK, exposed to UVB using the UVB-LEDs, as for Ca⁺⁺ imaging. Use of the UVB-LED device precluded application of a ET1 ELISA, only irradiated cells could be examined. Note the significant down-regulation of ET1 immunoreactivity by specific inhibition of TRPV4 (two different compounds, GSK205, RN1734), by PLC inhibition (U73122), also by inhibition of ET-convertase (CGS35066). (D) ET1 expression by UVB-exposed 1° MK depends on TRPV4 and PLC-quantification of immunocytochemistry. Densitometric measurements of n≧25 cells per condition, background subtracted, are shown, indicating a significant upregulation of ET1 in response to UVB (*p<0.05 ANOVA), and significant down-regulation vs. control-treated and UVB-exposed cells for treatments with selective TRPV4 antagonists (GSK205, RN1734), PLC-inhibitor U73122 and ET-convertase inhibitor CGS35066; *p<0.05, t-test; # p<0.05 ANOVA.

FIG. 9: UVB-evoked inflammasome activation in keratinocytes depends on TRPV4. (A) Caspase-1 immunolabeling in footpad skin in response to UVB. Representative images are from sections of skins before stimulation (control) or 48 hours post-UVB exposure. Bars=20 μm. (B) Quantifications of caspase-1 immunolabeling. Bar diagrams show densitometry, n≧3 animals/group. Comparisons: UVB exposed WT vs. Trpv4−/− and iKO+oil vs. iKO+tam. **p<0.01 ANOVA. (C) Western blotting for caspase-1 from 1° MK ±UVB-exposure. Note that caspase-1 levels, in particular cleaved caspase-1 (lower band), are elevated in UVB-exposed WT cells, but there is a complete absence of both procaspase-1 and cleaved caspase-1 in 1° MK from Trpv4−/− mice. (D) IL-1β is induced upon UVB-exposure and is dependent on TRPV4. Anti-IL-1β immunofluorescence, otherwise as in panel A. (E) Quantifications of IL-1β immunolabeling, n≧3 animals/group. Comparisons: UVB exposed WT vs. Trpv4−/− and iKO+oil vs. iKO+tam, ** p<0.01 ANOVA. (F) IL-1β concentrations in interstitial fluid of UVB-exposed footpad. IL-1β levels (ELISA) are shown in lavaged interstitial fluid. Note strong up-regulation in WT and oil-treated iKO mice after UVB, in contrast significant attenuation in Trpv4−/− and tam-treated iKO mice. n≧5 mice/group, ** p<0.01 ANOVA. (G) CXCL5 is induced upon UVB-exposure and is dependent upon TRPV4. Anti-CXCL5 immunolabeling, otherwise as in panel A. (H) Quantifications of CXCL5 immunolabeling, n≧3 animals/group. Comparisons: UVB exposed WT vs. Trpv4−/− and iKO+oil vs. iKO+tam, ** p<0.01 ANOVA.

FIG. 10: Epidermal TRPV4, ET1 and IL-1β are elevated in photodermatitis as compared to healthy human skin. (A) Representative micrographs of TRPV4, ET1 and IL-1β distribution in the epidermis of acute photodermatitis, as compared to healthy human skin. Immunostaining for each antigen is increased in acute photodermatitis vs. healthy skin. Scale-bars=50 μm (left), 100 μm (middle), 50 μm (right). (B) Morphometric analysis for immunoreactive TRPV4, ET1 and IL-1β. Findings reveal significantly increased immunolabeling for all three proteins in acute photodermatitis as compared to healthy human skin (n=3 subjects for normal, healthy skin, and 3 patients for acute UV photodermatitis).

FIG. 11: Exemplars of human chronic photodermatitis. Upper panel shows normal healthy human skin, as displayed in FIG. 10A, for comparison. Lower panel shows examples of chronic photodermatitis with elevated expression of TRPV4, in spinous and basal layers, ET1 (throughout) and IL-1β (throughout). In comparison to acute photodermatitis, note reduced interstitial intraepidermal edema. Bar=50 μm.

FIG. 12: External-topical application of a selective TRPV4 inhibitor attenuates UVB-evoked nocifensive behavior and inflammation. (A) UVB-induced nocifensive behavior. Pain behavior is attenuated by topical application of GSK205. The left-hand diagram shows withdrawal thresholds after UVB-exposure in response to noxious thermal cues (Hargreaves' test), and their modulation by two doses of topically applied GSK205 (1 mM and 5 mM; applied 60′ and 10′ pre-exposure). The higher dose led to a significant attenuation of thermal allodynia at 48 hours post-UVB; n=6 mice/group; ** p<0.01 ANOVA. The righthand diagram shows development of moderate thermal allodynia in Trpv4−/− mice, and similar sensitization for vehicle-treated vs. 5 mM GSK205-treated mice, indicating lack of off-target effects of the compound at 5 mM; n=5 mice/group. (B) GSK205-treatment attenuates keratinocyte expression of IL-1β in UVB-exposed footpad—representative micrographs. Bars=20 μm. (C) GSK205-treatment attenuates keratinocyte expression of IL-1β in UVB-exposed footpad quantifications. Bar diagrams show densitometry results from n=3 mice/group, ** p<0.01 ANOVA. (D) GSK205-treatment attenuates secretion of IL-1β by UVB-exposed 1° MK. IL-1β concentrations in supernatant (ELISA), are shown in response to UVB. Cells were cultured +/−5 μM GSK205. Note prevention of increase in IL-1β secretion in response to UVB upon treatment with GSK205. ** P<0.01 ANOVA.

FIG. 13: Topical application of a selective TRPV4 inhibitor attenuates UVB-evoked nocifensive behavior by suppressing upregulation of pro-algesic/algogenic mediators in murine keratinocytes—Findings for CXCL5 and IL6. (A) GSK205-treatment attenuates keratinocyte expression of CXCL5 in UVB-exposed footpad—micrographs and quantitation. As in FIG. 12B, specific immunolabeling for CXCL5, which is selectively upregulated in footpad keratinocytes in response to UVB, note attenuation with GSK205 treatment. Bar diagrams show densitometry of CXCL5 immunolabeling, n=3 animals per group, ≧3 sections analyzed per animal. Note significant differences for vehicle-treated mice between UVB-exposed and non-exposed, no such difference for mice treated topically with 5 mM GSK205. Comparison UVBexposed between vehicle and GSK205-treated, ** p<0.01 ANOVA. Bar=20 μm. (B) GSK205-treatment attenuates keratinocyte expression of IL-6 in UVB-exposed footpad—micrographs and quantification. As in FIG. 126 and FIG. 13A, specific immunolabeling for IL-6, demonstrates similar regulation of IL-6 as for CXCL5 and IL-1β. Comparison UVB-exposed between vehicle and GSK205-treated, ** p<0.01 ANOVA. Bar=20 μm.

FIG. 14: External-topical application of a selective TRPV4 inhibitor attenuates UVB-evoked nocifensive behavior and inflammation. (A) UVB-photodermatitis is attenuated in mice treated with GSK205. Representative H&E micrographs of paw-pad skin are shown, bars=20 μm. Treatment of UVB-exposed skin with GSK205 improved the skin architecture in mice as compared to vehicle-treated mice after 24 hours. (i) and (iii) Representative skin sections of UVB-induced photodermatitis after GSK205 treatment showed markedly reduced inflammatory infiltrate, less spongiosis and dermal-epidermal blisters with remaining epidermal thickening. (ii) and (iv) Vehicle-treated mice after UVB-induced photodermatitis were characterized by signs of severe acute photodermatitis such as spongiosis, epidermal hyperkeratosis, disrupted dermal-epidermal border (blister), and a marked inflammatory infiltrate with dilated blood vessels and dermal edema (arrows). Also note the erythrocyte accumulation in blood vessels indicative of dermatitis. (B) Topical treatment with a TRPV4-specific inhibitor attenuates upregulation of algogenic ET1/Edn1. Edn1 mRNA was determined by qPCR after extraction of total RNA from paw-pad epidermis. In vehicletreated skin, note increase of Edn1 expression with early up-regulation at the 2 hour time-point, and sustained elevation up to the 24 hour time-point. This time-course resembles that seen in WT control mice, when comparing to Trpv4−/− (FIG. 15). Importantly, topical treatment with 5 mM GSK205 results in complete lack of this regulation; n=4 mice/group, *p<0.05 ANOVA. (C) GSK205 does not function as sunscreen. Schematic illustrates the experimental set-up. (D) GSK205 does not function as sunscreen. The bar diagram shows results from n=7-8 mice/group, note absence of a change in UVB permeation with 5 mM GSK205, topically applied as for (B), vs. vehiclecontrol, yet significantly reduced with sunscreen SPF100.

FIG. 15: Upregulation of ET1/End1 in mouse paw in response to UVB. Edn1 mRNA was determined by qPCR after isolation of total RNA from paw-pad epidermis. Note the early increase, at the 2 hour time-point, in WT control epidermis, and its complete lack in Trpv4−/−, and sustained upregulation at 24 hours, slightly reduced vs. 2 hour time-point, again complete lack of upregulation in Trpv4−/−. Quantifications are for n=4 mice/group. ** denotes statistically significant (p<0.01, t-test).

FIG. 16: Skin UVB permeability testing. (A) Experimental set-up for testing of skin permeability to UVB. (B) Results from A. Note that intensity is 70% within 500 μm radius to the center of the UV beam.

FIG. 17: Role of TRPV4 in itch transmission in mice in vivo. Histamine (10%) was injected intracutaneously into the cheek of C57b/6 control (WT) or TRPV4 knockout mice (Trpv4 pan-knockout; n=6 per group). Over 30 min, TRPV4 null mice showed a significant reduction ((p<0.01) t-test)) of itch-behavior as compared to WT mice.

DETAILED DESCRIPTION

In a broad sense, the disclosure relates to compositions and methods for treating and/or preventing a dermatological disorder. The skin functions as an essential barrier between the external environment and the vertebrate organism. Keratinocytes in the skin absorb UV-light, leading to skin inflammation, pain, and itch after over-exposure, subsequently to skin pigmentation. The inventors have identified that the skin, in particular its epidermal epithelia, is more substantially involved in sensory transduction. For this, the inventors used a mouse model of sunburn in order to induce a state of lowered sensory thresholds evoked by a limited, self-resolving inflammation in response to UV spectrum of light. UV-evoked lowering of sensory thresholds shares major hallmarks of pathological pain, which is another valuable feature of this model.

The compositions and methods disclosed herein relate to the identification and characterization that epidermal keratinocytes function prominently to orchestrate UVB-mediated inflammation and sensitization of peripheral nerve endings in the skin, and in that respect, epidermal keratinocytes have a role similar to a co-sensory cell. Keratinocytes abundantly express the cation channel protein TRPV4, and the inventors have determined that TRPV4, expressed in epidermal keratinocytes, plays a role in UV-induced inflammation and pain. The channel exerts its role as a master regulator of UVB-evoked skin inflammation and nociception through Ca++ influx into keratinocytes. This UVB-evoked, TRPV4-mediated Ca++ influx re-programs the keratinocyte to function in a pro-inflammatory and pro-algesic (pro-pain) manner, via TRPV4-dependent secretion of endothelin-1, which may lead to sensation of itch and skin pigmentation. TRPV4 is activated contemporaneously with UVB exposure, which leads to activation of pro-algesic pathways via secreted factors previously demonstrated to have relevance in human pain. As disclosed in further detail herein, mice with inducible Trpv4 deletions targeted to keratinocytes were induced for TRPV4 deletion, subsequently UVB-exposed, and found to be less sensitive to noxious thermal and mechanical stimulation than control mice. Epidermal TRPV4 was identified as a protein involved in the orchestration of UVB-mediated skin inflammation. In mouse skin, UVB-evoked inflammasome activation and increased expression of pro-algesic/algogenic mediators, such as IL1-β, CXCL5, ET-1, and IL-6, were TRPV4-dependent. ET-1 has been shown in humans to not only elicit painful sensations, but to also elicit itch, when injected into the skin. Also, ET-1 has been identified as a melanogen, that is, to increase skin pigmentation by signaling to melanocytes. In primary murine keratinocytes, UVB caused a direct, TRPV4-dependent Ca⁺⁺-response. Moreover, in mice, topical application of a TRPV4-selective inhibitor reduced UVB-evoked epidermal inflammation and pain behavior. Additionally, it was found that epidermal expression of TRPV4, ET1, and IL1β were increased in acute human UV-photodermatitis. The term photodermatitis is used in this application referring to skin inflammation in response to UV radiation/light. This tissue response can include pain, irritation, itch, influx of inflammatory and pain-enhancing cells and tissue injury.

The dermatological disorder may be associated with the TRPV4 pathway. Dermatological disorders include, but are not limited to, photo-induced inflammation, pain in diseases involving skin pain, itch, cancer, autoimmune diseases, fibrotic diseases, other acneiform or inflammatory skin diseases, and pigmentation disorders. For example, dermatological disorders may include, but are not limited to, sunburn; photoallergic reaction; phototoxic reaction; phytophotodermatitis (Berloque dermatitis); acute and chronic actinic dermatitis; atopic dermatitis exacerbation; all subtypes of rosacea including trigeminal-pain associated rosacea; all lupus erythematosus subtypes (systemic, discoid, subacute); atopic dermatitis; actinic prurigo; prurigo nodularis; prurigo subacuta; prurigo pigmentosa; Lichen simplex (also called neurodermatitis); diabetic pruritus; uremic pruritus; pruritus induced by metabolic (liver) diseases; pruritus induced by malignancies like lymphoma; pruritus induced by polycythemia vera; pruritus induced by scabies; pruritus induced by bullous pemphigoid; pruritus induced by urticaria (especially but not exclusively actinic urticaria); pruritus induced by insect/arachnoid vector bite; pruritus induced by parasitosis; melanoma; non-melanoma skin cancer (BCC, SCC); actinic keratosis and other premalignant skin cancers; mycosis fungoides; Sézary syndrome; Xeroderma pigmentosum; Cockayne syndrome; all lupus erythematosus subtypes (systemic, discoid, subacute); dermatomyositis; erythema multiforme; lichen planus; fibrotic diseases induced by UV-exposure (Rhinophyma, chronic actinic dermatitis, actinic reticuloid, photoaging, hyalinosis cutis et mucosae; polymorph light eruption; Acne aestivalis; all porphyria subforms with implications on photo-induced skin changes (erythropoetic porphyria, erythropoetic protoporphyria, Porphyria variegate); photo-induced Herpes simplex infection (Herpes labialis); morbus Darier; disseminated superficial actinic porokeratosis; pityriasis rubra pilaris; Bloom syndrome; Rothmund-Thomson syndrome; Hartnup syndrome photoaging; wrinkles; photo-induced inflammation; pigmentation; and pigmentation disorders.

Methods

In an aspect, the disclosure provides methods of reducing skin inflammation in a subject in need thereof. The methods may comprise administering to the subject an effective amount of a TRPV4 inhibitor. The skin inflammation may be related to UVB exposure.

Skin inflammation may be associated with conditions including, but not limited to, sunburn (acute photodermatitis), photoallergic reaction, phototoxic reaction, phytophotodermatitis (Berloque dermatitis), acute and chronic actinic dermatitis, atopic dermatitis exacerbation, and rosacea.

In other aspects, the disclosure provides methods of pain management. The methods may comprise administering to at least a portion of the skin of a subject in need thereof an effective amount of a TRPV4 inhibitor. The pain may be related to UVB exposure.

Pain may be chronic or acute. Pain may be associated with or result from conditions including, but not limited to, all subtypes of rosacea including trigeminal-pain associated rosacea, and all lupus erythematosus subtypes (systemic, discoid, subacute).

In other aspects, the disclosure provides methods of reducing itch in a subject in need thereof. ET-1 has been shown to elicit itch, and as shown in the Examples, increased expression of ET-1 was TRPV4-dependent. The methods may comprise administering to the subject an effective amount of a TRPV4 inhibitor.

Itch may be chronic or acute. Itch may be associated with or result from conditions including, but not limited to, rosacea, atopic dermatitis, actinic prurigo, prurigo nodularis, prurigo subacuta, prurigo pigmentosa, Lichen simplex (also called neurodermatitis), diabetic pruritus, and uremic pruritus. Itch or pruritus may be associated with or result from conditions including metabolic (liver) diseases, malignancies like lymphoma, polycythemia vera, scabies, bullous pemphigoid, urticaria (especially but not exclusively actinic urticaria), insect/arachnoid vector bite, and parasitosis.

In other aspects, the disclosure provides methods of treating cancer in a subject in need thereof. The methods may comprise administering to the subject an effective amount of a TRPV4 inhibitor.

The cancer and related conditions may include, but are not limited to, melanoma, non-melanoma skin cancer (BCC, SCC), actinic keratosis and other premalignant skin cancers, mycosis fungoides, Sézary syndrome, and Xeroderma pigmentosum.

In other aspects, the disclosure provides methods of treating an autoimmune disease in a subject in need thereof. The methods may comprise administering to the subject an effective amount of a TRPV4 inhibitor.

Autoimmune diseases may include, but are not limited to, all lupus erythematosus subtypes (systemic, discoid, subacute), dermatomyositis, erythema multiforme, and lichen planus.

In other aspects, the disclosure provides methods of treating a fibrotic disease in a subject in need thereof. The methods may comprise administering to the subject an effective amount of a TRPV4 inhibitor.

Fibrotic diseases may include conditions induced by UV-exposure, such as, for example, Rhinophyma, chronic actinic dermatitis, actinic reticuloid, photoaging, and hyalinosis cutis et mucosae.

In other aspects, the disclosure provides methods of treating other acneiform or inflammatory skin disease in a subject in need thereof. The methods may comprise administering to the subject an effective amount of a TRPV4 inhibitor.

Acneiform or inflammatory skin diseases may include, but are not limited to, polymorph light eruption, Acne aestivalis, photo-induced Herpes simplex infection (Herpes labialis), morbus Darier, disseminated superficial actinic porokeratosis, Pityriasis rubra pilaris, and all porphyria subforms with implications on photo-induced skin changes such as, for example, erythropoetic porphyria, erythropoetic protoporphyria, and Porphyria variegate.

In other aspects, the disclosure provides methods of reducing skin pigmentation in a subject in need thereof. ET-1 has been shown to signal to skin melanocytes and function as a major melanogen (=enhancing skin pigmentation), and as shown in the Examples, increased expression of ET-1 was TRPV4-dependent. The methods may comprise administering to the subject an effective amount of a TRPV4 inhibitor.

Skin inflammation, pain, itch, and/or pigmentation may also be associated with disorders including, but not limited to, Cockayne syndrome, non-UV skin burn less than 3^(rd) degree, disturbed wound healing, exposure and pathological response to poison ivy, and pain of bone fractures directly adjacent to the skin such as fractures of the tibia, digits, or skull.

In other aspects, the disclosure provides methods of preventing dermatological diseases or disorders such as irritation, pain, itch, pruritus, autoimmune diseases, skin cancer (including melanoma, for example, with topical treatment of TRPV4 inhibitor-based UV protection), autoimmune diseases, fibrotic disorders, pigmentation disorders, and others as described above. In some embodiments, the disclosure provides methods of preventing the development and/or exacerbation of Xeroderma pigmentosum, Cockayne syndrome, Bloom syndrome, Rothmund-Thomson syndrome, and Hartnup syndrome.

In other aspects, the disclosure provides methods of treating or preventing cosmetic conditions. For example, the disclosure provides methods of treating or preventing photoaging, wrinkles, photo-induced inflammation, pigmentation, and pigmentation disorders.

TRPV4 Inhibitor

As TRPV4 is a Ca²⁺-permeable, nonselective cation channel, some embodiments provide for a TRPV4 inhibitor that can inhibit the biological function of TRPV4 (e.g., inhibit cation channel activity, inhibit Ca++ transport and/or availability). Other embodiments provide for a TRPV4 inhibitor that may inhibit the expression of mRNA encoding TRPV4. Some embodiments provide a TRPV4 inhibitor that may inhibit the translation of mRNA encoding TRPV4 to protein. Thus, a TRPV4 inhibitor may indirectly or directly bind and inhibit the activity of TRPV4 (e.g., binding activity or enzymatic activity), reduce the expression of TRPV4, prevent expression of TRPV4, or inhibit the production of TRPV4 in a cell. Inhibit or inhibiting relates to any measurable reduction or attenuation of amounts or activity, e.g., amounts or activity of TRPV4, such as those disclosed herein.

In some embodiments, a TRPV4 inhibitor can increase the amount of, or the biological activity of a protein that can reduce the activity of TRPV4. Agents capable of increasing the level of such a protein may include any agent capable of increasing protein or mRNA levels or increasing the expression of the protein. In one embodiment, a TRPV4 inhibitor may comprise the protein itself. For example, a TRPV4 inhibitor may include exogenously expressed and isolated protein capable of being delivered to the cells. The protein may be delivered to cells by a variety of methods, including fusion to Tat or VP16 or via a delivery vehicle, such as a liposome, all of which allow delivery of protein-based agents across the cellular membrane. Those of skill in the art will appreciate that other delivery mechanisms for proteins may be used. Alternatively, mRNA expression may be enhanced relative to control cells by contact with a TRPV4 inhibitor. For example, the agent capable of increasing the level of natively expressed protein may include a gene expression activator or de-repressor. As another example, a TRPV4 inhibitor capable of decreasing the level of natively expressed protein may include a gene expression repressor. An agent capable of increasing the level of protein may also include agents that bind to directly or indirectly and increase the effective level of protein, for example, by enhancing the binding or other activity of the protein. The agent capable of decreasing the level of protein may also include agents that bind to directly or indirectly and decrease the effective level of protein, for example, by inhibiting or reducing the binding or other activity of the protein.

The amount or level of expression of a biomolecule (e.g., mRNA or protein) in a cell may be evaluated by any variety of techniques that are known in the art. Thus, inhibit or inhibiting, such as, for example, the level of protein expression (e.g., TRPV4), may be evaluated at either the protein or mRNA level using techniques including, but not limited to, Western blot, ELISA, Northern blot, real time PCR, immunofluorescence, or FACS analysis. For example, the expression level of a protein may be evaluated by immunofluorescence by visualizing cells stained with a fluorescently-labeled protein-specific antibody, Western blot analysis of protein expression, and RT-PCR of protein transcripts. The expression level of TRPV4 may be compared to a control. A control may include comparison to the level of expression in a control cell, such as a non-disease cell or other normal cell. Alternatively a control may include an average range of the level of expression from a population of normal cells. Alternatively, a standard value developed by analyzing the results of a population of cells with known responses to therapies or agents may be used. Those skilled in the art will appreciate that a variety of controls may be used.

A TRPV4 inhibitor may comprise a variety of compounds and compositions and agents. For example, a TRPV4 inhibitor may comprise a compound. A TRPV4 inhibitor may comprise a biological molecule, including nucleic acid molecules, such as a polynucleotide having RNAi activity against TRPV4 or a substrate thereof. In embodiments, the nucleic acid molecules can include decoy RNAs, dsRNAs, miRNAs, siRNAs, nucleic acid aptamers, antisense nucleic acid molecules, and enzymatic nucleic acid molecules that comprise a sequence that is sufficient allow for binding to an encoding nucleic acid sequence and inhibit activity thereof (i.e., are complementary to such encoding nucleic acid sequences). Suitably, an RNAi molecule comprises a sequence that is complementary to at least a portion of a target sequence such that the RNAi can hybridize to the target sequence under physiological or artificially defined (e.g., reaction) conditions. In some embodiments an RNAi molecule comprises a sequence that is complementary such that the molecule can hybridize to a target sequence under moderate or high stringency conditions, which are well known and can be determined by one of skill in the art. In some embodiments an RNAi molecule has complete (100%) complementarity over its entire length to a target sequence. A variety of RNAi molecules are known in the art, and can include chemical modifications, such as modifications to the sugar-phosphate backbone or nucleobase that are known in the art. The modifications may be selected by one of skill in the art to alter activity, binding, immune response, or other properties. In some embodiments, the RNAi can comprise an siRNA having a length from about 18 to about 24 nucleotides.

In some embodiments, the inhibitory nucleic acid molecule can bind to a target nucleic acid sequence under stringent binding conditions. The terms “stringent conditions” or “stringent hybridization conditions” includes reference to conditions under which a polynucleotide will hybridize to its target sequence, to a detectably greater degree than other sequences (e.g., at least 2-fold over background). An example of stringent conditions include those in which hybridization in 50% formamide, 1 M NaCl, 1% SDS at 37° C., and a wash in 0.1×SSC at 60 to 65° C. is performed. Amino acid and polynucleotide identity, homology and/or similarity can be determined using the ClustalW algorithm, MEGALIGN™ (Lasergene, WI). Given a target polynucleotide sequence, for example of TRPV4 or biological substrate thereof, an inhibitory nucleic acid molecule can be designed using motifs and targeted to a region that is anticipated to be effective for inhibitory activity, such as is known in the art.

In other embodiments, a TRPV4 inhibitor comprises an antibody that can specifically bind to a protein such as TRPV4 or a fragment thereof. Embodiments also provide for an antibody that inhibits TRPV4 through specific binding to a TRPV4 substrate molecule. The antibodies can be produced by any method known in the art, such as by immunization with a full-length protein such as TRPV4, or fragments thereof. The antibodies can be polyclonal or monoclonal, and/or may be recombinant antibodies. In embodiments, antibodies that are human antibodies can be prepared, for example, by immunization of transgenic animals capable of producing a human antibody (see, for example, International Patent Application Publication No. WO 93/12227). Monoclonal antibodies (mAbs) can be produced by a variety of techniques, including conventional monoclonal antibody methodology, e.g., the standard somatic cell hybridization technique of Kohler and Milstein, and other techniques, e.g., viral or oncogenic transformation of B-lymphocytes. Animal systems for preparing hybridomas include mouse. Hybridoma production in the mouse is very well established, and immunization protocols and techniques for isolation of immunized splenocytes for fusion are well known in the art. Fusion partners (e.g., murine myeloma cells) and fusion procedures are also known.

Any suitable methods can be used to evaluate a candidate active agent for inhibitory activity toward TRPV4. Such methods can include, for example, in vitro assays, in vitro cell-based assays, ex vivo assays, and in vivo methods. The methods can evaluate binding activity, or an activity downstream of the enzyme of interest. Ex vivo assays may involve treatment of cells with an agent of the invention, followed by detection of changes in transcription levels of certain genes, such as TRPV4 through collection of cellular RNA, conversion to cDNA, and quantification by quantitative real time polymerase chain reaction (RT-QPCR). Additionally, the cell viability or inflammation may be determined after treatment with an agent.

In certain embodiments, the TRPV4 inhibitor is according to Formula I:

wherein A, B, and C are independently selected from the group consisting of aromatic, heteroaromatic, cycloalkenyl, and heterocycloalkenyl groups;

D is C₁-C₃ alkylene;

E is a bond, or C₁-C₂ alkylene; and

R is selected from the group consisting of hydrogen, hydroxyl, amino, alkyl, alkenyl, heteroalkyl, aromatic ring, or heteroaromatic ring. In some embodiments, B and C are independently a phenyl group. In some embodiments, A is phenyl or heteroaryl. In some embodiments, A is pyridnyl. In some embodiments, R is C1-C4 alkyl. In some embodiments, A is heteroaryl, B and C are phenyl, D is ethylene, E is methylene, and R is methyl. In some embodiments, R is ethyl.

In certain embodiments, the TRPV4 inhibitor comprises the following compound:

In certain embodiments, the TRPV4 inhibitor comprises the following compound:

In certain embodiments, the TRPV4 inhibitor comprises the following compound:

In some embodiments, the disclosure provides a method of treating a subject wherein the method comprises administering an inhibitor of TRPV4 in a pharmaceutically acceptable composition.

In other aspects, the disclosure provides compositions comprising a TRPV4 inhibitor.

“Administration” or “administering” refers to delivery of a compound or composition by any appropriate route to achieve the desired effect. Administration may include any convenient route of administration, whether systemically/peripherally or at the site of desired action, including but not limited to, oral (e.g. by ingestion); topical (including e.g. transdermal, intranasal, ocular, buccal, and sublingual); pulmonary; respiratory (e.g. by inhalation or insufflation therapy using, e.g. an aerosol, e.g. through mouth or nose); rectal; vaginal; parenteral, for example, by injection, including subcutaneous, intradermal, intramuscular, intravenous, intraarterial, intracardiac, intrathecal, intraspinal, intracapsular, subcapsular, intraorbital, intra peritoneal, intratracheal, subcuticular, intraarticular, subarachnoid, and intrasternal; by implant of a depot, for example, subcutaneously or intramuscularly. In certain embodiments, administration may be topical. “Co-administered” refers to simultaneous or sequential administration. A compound or composition may be administered before, concurrently with, or after administration of another compound or composition.

One skilled in the art can select an appropriate dosage and route of administration depending on the patient, the particular disease, disorder, or condition being treated, the duration of the treatment, concurrent therapies, etc. In certain embodiments, a dosage is selected that balances the effectiveness with the potential side effects, considering the severity of the disease, disorder, or condition (e.g., skin inflammation, pain, or itch).

“Pharmaceutically acceptable” means suitable for use in a human or other mammal. The terms “pharmaceutically acceptable carriers” and “pharmaceutically acceptable excipients” are used interchangeably and refer to substances that are useful for the preparation of a pharmaceutically acceptable composition. In certain embodiments, pharmaceutically acceptable carriers are generally compatible with the other ingredients of the composition, not deleterious to the recipient, and/or neither biologically nor otherwise undesirable.

The composition may comprise the TRPV4 inhibitor in combination with a carrier, vehicle, or diluent. Embodiments provide for pharmaceutically acceptable carriers including, but not limited to, substances useful for topical, intrathecal, ocular, parenteral, intravenous, intraperitoneal intramuscular, sublingual, nasal, and oral administration. Administration may be systemic. “Pharmaceutically acceptable carrier” also includes agents for preparation of aqueous dispersions and sterile powders for injection or dispersions. Examples of pharmaceutically acceptable carriers and excipients are discussed, e.g., in Remington Pharmaceutical Science, 16th Ed. Certain exemplary techniques and compositions for making dosage forms are described in the following references: Modern Pharmaceutics, Chapters 9 and 10, Banker & Rhodes, eds. (1979); Lieberman et al., Pharmaceutical Dosage Forms: Tablets (1981); and Ansel, Introduction to Pharmaceutical Dosage Forms, 2nd Ed., (1976). The carrier, vehicle, or diluent may be suitable for topical application.

In certain embodiments, compositions are formulated for topical administration. For compositions suitable for topical administration, the composition may be combined with one or more carriers and used in the form of cosmetic formulations. Formulations may include a foam, cream, gel, lotion, ointment, or solution. For example, a TRPV4 inhibitor may be suitably dissolved in the alcohol of skin disinfectant gel or in lotions, creams, or other formulations. In certain embodiments, a TRPV4 inhibitor may be included in or added to a cosmetic formulation. In certain embodiments, a TRPV4 inhibitor may be included in or added to sun protection topical formulations.

For oral therapeutic administration, the composition may be combined with one or more carriers and used in the form of ingestible tablets, buccal tablets, troches, capsules, elixirs, suspensions, syrups, wafers, chewing gums, foods, and the like. The percentage of the compositions and preparations may, of course, be varied and may conveniently be between about 0.1 to about 100% of the weight of a given unit dosage form. The tablets, troches, pills, capsules, and the like may also contain the following: binders such as gum tragacanth, acacia, corn starch or gelatin; excipients such as dicalcium phosphate; a disintegrating agent such as corn starch, potato starch, alginic acid and the like; a lubricant such as magnesium stearate; and a sweetening agent such as sucrose, fructose, lactose or aspartame or a flavoring agent such as peppermint, oil of wintergreen, or cherry flavoring. The above listing is merely representative and one skilled in the art could envision other binders, excipients, sweetening agents and the like. When the unit dosage form is a capsule, it may contain, in addition to materials of the above type, a liquid carrier, such as a vegetable oil or a polyethylene glycol. Various other materials may be present as coatings or to otherwise modify the physical form of the solid unit dosage form. For instance, tablets, pills, or capsules may be coated with gelatin, wax, shellac or sugar and the like.

“Effective amount” refers to a dosage of a compound or composition effective for eliciting a desired effect, commensurate with a reasonable benefit/risk ratio. This term as used herein may also refer to an amount effective at bringing about a desired in vivo effect in an animal, preferably, a human, such as reduction in skin inflammation, reduction in pain, or reduction in itch.

The amount of a TRPV4 inhibitor in such therapeutically useful compositions is such that an effective dosage level will be obtained. The selected dosage level will depend upon a variety of factors including the activity of the particular compound employed, the route of administration, the time of administration, the rate of excretion or metabolism of the particular compound being employed, the duration of the treatment, other drugs, compounds and/or materials used in combination with the particular compound employed, the age, sex, weight, condition, general health and prior medical history of the patient being treated, and like factors well known in the medical arts.

In general, the daily dose contains from about 0.1 mg to about 2000 mg of the active ingredient, or about 0.5 to about 60 mg of the active ingredient. This dosage form permits the full daily dosage to be administered in one or two oral doses. More than once daily or twice daily administrations, e.g., 3, 4, 5, or 6 administrations per day, are also contemplated herein.

In some embodiments, as noted above, administering relates to providing an amount effective at bringing about a desired in vivo effect such as inhibition of TRPV4 in an animal, such as a human. As used herein, a “subject in need of treatment” refers to a subject having been diagnosed with a dermatological disease or disorder associated with skin inflammation, pain, itch, or a combination thereof. A subject may be a mammalian subject. In embodiments a subject can include human and non-human animals. The term “non-human animals” includes all vertebrates, e.g., non-mammals (such as chickens, amphibians, reptiles) and mammals, such as non-human primates, domesticated and/or agriculturally useful animals (such as sheep, dogs, cats, cows, pigs, etc.), and rodents (such as mice, rats, hamsters, guinea pigs, etc.). Accordingly, embodiments of the methods described herein relate to treatment of a cell or tissue, a cell or tissue from a subject, or a subject that may be a eukaryote, an animal, a vertebrate animal, a mammal, a rodent (e.g., a guinea pig, a hamster, a rat, a mouse), murine (e.g., a mouse), canine (e.g., a dog), feline (e.g., a cat), equine (e.g., a horse), a primate, simian (e.g., a monkey or ape), a monkey (e.g., marmoset, baboon), an ape (e.g., gorilla, chimpanzee, orangutan, gibbon), or a human.

In other aspects, the disclosure provides a transgenic mouse whose genome comprises deletions of the Trpv4 gene in keratinocytes of the epidermis. The transgenic mouse may be a knockout for the Trpv4 gene in keratinocytes of the epidermis following keratinocyte-specific activation and expression of a site-specific recombination enzyme. Knockout of the Trpv4 gene may be carried out by any suitable means known in the art. For example, the transgenic mouse may be generated by Keratin-14 promoter expression of a site-specific recombination enzyme. Site-specific recombination enzymes may include CRE recombinase. The site-specific recombination enzyme may be fused to a mutated estrogen receptor. An anti-estrogen may have increased affinity to the mutated estrogen receptor relative to wild-type estrogen. The anti-estrogen may comprise tamoxifen. In some embodiments, addition of the anti-estrogen to the transgenic mouse drives the site-specific recombination enzyme to the nucleus and results in knockdown of expression of the Trpv4 gene. As such, the keratinocyte-specific deletion of the Trpv4 gene may be induced by applying an anti-estrogen. In some embodiments, deletion of the Trpv4 gene can be specifically and conditionally induced in keratinocytes of the epidermis. In some embodiments, deletion of the Trpv4 gene may be achieved by expression of a constitutively active or inducible recombination enzyme in keratinocytes of the epidermis. In some embodiments, the transgenic mouse may exhibit reduced expression relative to a control of at least one of IL6, ET1, caspase1, IL1β, and CXCL5, or a combination thereof, in response to UVB exposure.

In a further aspect, the disclosure provides methods for identifying a selective inhibitor of TRPV4. The methods may include (a) contacting a mouse with a test compound; (b) determining a biological activity of TRPV4 after contacting with the test compound; and (c) determining a control level of biological activity of TRPV4 in the absence of the test compound; (d) comparing the biological activity of TRPV4 from step (b) with the biological activity of TRPV4 from a model of TRPV4 deletion, wherein the model of TRPV4 deletion includes the transgenic mouse as disclosed herein or a pan-null Trpv4−/− mouse; and (e) identifying the test compound as a selective inhibitor of TRPV4 when at least one of (i) the TRPV4 biological activity is lower in the presence of the test compound than the TRPV4 biological activity in the absence of the test compound; (ii) the TRPV4 biological activity in the presence of the test compound is about the same as, or lower than, the TRPV4 biological activity in the model of TRPV4 deletion; or (iii) any combination of (i) and (ii).

The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including but not limited to”) unless otherwise noted. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to illustrate aspects and embodiments of the disclosure and does not limit the scope of the claims.

EXAMPLES Example 1: Materials and Methods

Animals

The Trpv4 genomic locus was engineered so that loxP sites surrounded exon13 which encodes TM5-6. This mutation was propagated in mice which were crossed to K14-CRE-ERtam mice, so that ((Trpv4lox/lox)×(K14-CRE-ERtam))-mice could be induced by tamoxifen administration via oral gavage for 5 consecutive days at 6 mg/day in 0.3 mL cornoil, at age 2-4 months of age, plus a one-time booster two weeks after the last application. Male and female mice were induced equally. Efficiency of knockdown was verified by qRT-PCR for Trpv4 using primers sense 5′-CCTGCTGGTCACCTACATCA (SEQ ID NO: 1) and antisense 5′-CTCAGGAACACAGGGAAGGA (SEQ ID NO: 2), with the former primer located in exon 13. All animal experimentation described here was conducted in full compliance with NIH and Duke University internal guidelines, and under a valid IACUC protocol.

Using the same genomic clone that was used for generating the Trpv4−/− pan-null mouse, the Trpv4 targcting construct was electroporated into mouse ES cells (C57BL6 background), and orthotopic integration was verified by PCR and Southern blot. The engineered mutation was introduced into the germline by mating of chimeric mice with C57BL6 WT mice. The selection marker was deleted by FLPemediated excision of the frt-pGK-neo-frt cassette in FLPe deleter mice. Genotyping was accomplished by PCR and subsequent PacI digest (FIG. 1B).

Behavioral Assessment of Withdrawal Thresholds

Behavioral tests were performed to evaluate the decrease in withdrawal thresholds in response to mechanical von Frey hair or thermal stimuli applied to hind paws. Tests were conducted. These withdrawal thresholds were ascertained before and after UV exposure. Mice were exposed using a Bio Rad Gel Doc 2000 UV transilluminator (302 nm) for 5 minutes with an exposure of 600 mJ/cm², 3-5 days after the last application of tamoxifen/oil.

Paw Interstitial Fluid Analysis

48 hours after UV exposure, each animal received an intraplantar injection of 10 μL PBS directly posteuthanasia. The interstitial fluid was immediately collected and analyzed by ELISA (Biorad) for presence of IL-1β.

In-Vivo Topical Interventions

ET1 injections: After determining base-line withdrawal thresholds, each animal received an intraplantar injection of 10 μL 100 nM ET-1 plus contralateral vehicle. Thresholds were again evaluated 1 hour after injection.

GSK205 topical treatment: A viscous solution of 68% EtOH/5% glycerol plus 1 mM or 5 mM GSK205 (none for control) was applied to hindpaws by rubbing in 20 μL, applied at time-points 1 hour and again 10 min before UV exposure.

Formalin-induced nocifensive behavior: 4% formalin was injected into the right hindpaw. Mice were then videotaped for 50 mins and behavior analyzed by blinded observers.

Mouse Tissue Processing for 1 μm Semithin Sections and EM

Samples were processed and subjected to EM.

Mouse and Human Tissue Processing for Immunohistochemistry

Routine procedures were followed, and human tissue was processed under institutional review-board approval (UCSF).

Primary Mouse Keratinocyte Cell Culture

Primary mouse keratinocytes were derived from back skin of newborn mice.

Analysis of IL-1β Secreted by Cultured Keratinocytes after UV Exposure

Before UV irradiation, culture media was replaced with PBS. The cells were then irradiated at a dose of 50 mJ/cm² with UVB. 24 hours later, supernatants were assayed using IL-1β ELISA (R&D Systems, Minneapolis, Minn.).

Ca++ Imaging of Cultured Keratinocytes

Ca++ imaging of 1° MK was conducted following routine procedures. For UVB stimulation, a customized device was built. The system comprised a printed circuit board for electrical interconnects and mechanical support and an ultraviolet light-emitting diode (UV LED). Customized provisions at the cellular end included a quartz coverslip as the bottom of the cell culture dish plus a thermal equilibration stage (HW-101 Dagan Corporation), fitted to an Olympus BX61 upright microscope. The UV LED was a III-nitride-based type (UVTOP-295 BL; Sensor Electronic Technology).

The operating wavelength was 295 nm (FIG. 2A), with a full-width half-max of 12 nm. The optical power was 500 mW. The focal point was aimed at the plane of the upper surface of the quartz coverslip, which was used to minimize UV absorption along the optical path towards the cells (FIG. 2A-C). The optical intensity at the focal point was estimated to be 150 mW/mm².

Keratinocyte UV Irradiation Using 295 nm LED and Immunocytochemistry

1° MK were exposed to UVB using the UV optical system (295 nm LED). 24 hours later the cells were fixed and fluorescently immunolabeled for ET1. Digital images were captured and subjected to morphometry.

Statistical Analysis

Numeric signals or values were averaged for their respective groups and the statistical mean+/−standard error of the mean were compared between groups by using a fixed-effect one-way ANOVA and post-hoc Scheffe test or Student's t-test, at a significance level of p<0.05.

Chemicals/Biologicals

The following biologicals and compounds were used: Endothelin1; BQ123 and BQ788 (ET(R) blockers for ET(R)-A and ET(R)-B; Sigma, St. Louis, Mo.), U73122 (PLC inhibitor; Tocris, Ellisville, Mo.), 4α-phorbol 12,13 didecanoate (4α-PDD; TRPV4 activator; Tocris), GSK205 (TRPV4 inhibitor (Li et al., 2011; Phan et al., 2009; Vincent and Duncton, 2011)), RN-1734 (TRPV4 inhibitor; Tocris), CGS35066 (endothelin-converting enzyme inhibitor, Tocris), isopentenyl pyrophosphate, IPP (TRPV3 inhibitor; Sigma); and Camphor (TRPV3 activator; Whole Foods).

Behavioral Assessment of Withdrawal Thresholds and Nocifensive Behavior

Behavioral tests were performed to evaluate the decrease in withdrawal thresholds in response to mechanical or thermal stimuli applied to hind paws. These withdrawal thresholds were ascertained before and after UVB exposure. Mice were confined by plexi-glass enclosures on top of 25×26 cm Bio Rad Gel Doc 2000 UV transilluminator (302 nm), and otherwise allowed to openly explore this environment. UV-exposure lasted for 5 minutes with an exposure of 600 mJ/cm². Careful observations upon initiation of this method demonstrated that hindpaws were exposed to UV throughout this period.

Automated Von Frey Hair Testing

Hindpaw mechanical withdrawal thresholds were determined by the automated von Frey hair method, using a 0.5 mm diameter stainless steel filament, part of an automated plantar touch stimulator (Ugo Basile, Modena, Italy). Relevant detail included pre-test acclimatization in a quiet room for 30 min, conducting the test at the same time of day and blinded observers. The stimulus was delivered to the hindpaw, automatically discontinued upon withdrawal, and its intensity recorded automatically. 6-8 trials per animal were conducted, with equal exposure of both hindpaws, leading to an average withdrawal threshold. Results are reported as A-threshold, which was calculated by subtracting post-treatment from pre-treatment measurements, expressed as % or relative to 1.0.

Hargreaves' Test

Hindpaw thermal (hot) withdrawal thresholds were determined by the well-established Hargreaves' method, using an infra-red thermal stimulation device that delivers the stimulus from underneath the hindpaw combined with automatic shut-off upon withdrawal (Ugo Basile). Stimulation and measurements were conducted as described for von Frey hair testing. A cutoff of 20 sec was set to prevent tissue damage.

Formalin-Induced Nocifensive Behavior

Videos were read by blinded observers for the total amount of time each mouse spent flinching or licking the injected hindpaw.

Mouse Tissue Processing for 1 μm Semithin Sections and Electron Microscopy

Samples were fixed in 2% glutaraldehyde, 4% PFA, and 2 mM CaCl₂ in 0.05 M sodium cacodylate buffer, pH 7.2, at room temperature for >1 h, dehydrated, postfixed in 1% osmium tetroxide, and processed for Epon embedding. Semi-thin sections (1 μm) were stained with toluidine blue and photographed with an Axioplan 2 microscope (Zeiss). For EM analysis, ultrathin sections (60-70 nm) were counterstained with uranyl acetate and lead citrate. EM images were taken with a transmission electron microscope (Tecnai G2-12; FEI) equipped with a digital camera (model XR60; Advanced Microscopy Techniques, Corp.).

Mouse Tissue Processing for Immunohistochemistry

Routine procedures were followed as described previously (Chen et al., 2009). Mice were perfused transcardially with 30 mL PBS, followed by 30 mL 4% paraformaldehyde. Tissues, including the L5 DRGs (bilateral), and footpad preparations, were dissected and postfixed in 4% paraformaldehyde. Tissue blocks were further cryoprotected in 30% sucrose in PBS for 24-48 hours. For mouse TRPV4, keratin-specific antibodies, phospho-ERK, IL-6, IL-1β, CXCL5 and caspase-1, tissue was prepared as frozen blocks and subsequently sectioned on a cryostat. For CD68, CD15 (neutrophil elastase) and CD3, mouse skin was prepared by 2% PFA perfusion. Footpad and DRG sections (both at 6-10 μm) were thaw-mounted, blocked with 5% normal goat serum (NGS; Jackson), then incubated overnight at 4° C. with the following primary antibodies: rabbit anti-TRPV4 (1:300; Abcam), mouse anti-keratin 14 (1:300; Abcam against C-terminal peptide beyond residue 850); rabbit anti-keratin 14 (1:1000; Fuchs-Lab), rabbit anti-phosph-ERK1/2 (1:500; Cell signaling technologies), goat anti-IL-1β (1:800; Abcam), goat anti-IL-6 (1:200; Santa Cruz Biotechnology Inc); rabbit anti-caspase-1 (1:200; Biovision Research Products, CA); goat anti-mouse LIX/CXCL5 (1:200; R&D Systems Inc), anti-CD68, anti-CD25 and anti-CD3 (AbDSerotec). Immunodetection was accomplished with appropriate fluorescently-labeled secondary antibodies (AlexaFluor595, AlexaFluor488-conjugated antibodies at 1:600; Invitrogen; for CD15 biotinylated secondary antibody from donkey, 1:400 followed by rhodamine-streptavidine 1:250), or with peroxidase-linked detection reagents (for CD68) for 2 hours at room-temperature. Sections were rinsed, mounted, and cover-slipped with fluoromount (Sigma). Digital micrographs were obtained using a BX61 Olympus upright microscope, also with a Zeiss LSM510 confocal, both equipped with high-res CCD camera, and acquired with constant exposure settings, using ISEE or Zeiss Zen software. Morphometric analysis was conducted using ImageJ freeware (v1.45) with tailored regions-of-interest that spared the nuclear compartment. ImageJ was also used for determination of DRG surface area.

Human Tissue Specimens Immunolabeling

Human tissue was deparaffinized with xylene and ethanol series, then washed in PBS, and incubated at 80° C. for 20 min in Antigen Retrieval buffer (Biogenex). Subsequently, specimens were washed in PBS. Endogenous peroxidase was blocked with 0.3% H₂O₂+0.01% sodium azide in PBS for 10 min at room temperature, followed by washing steps in PBS. Blocking was performed in 5% normal horse serum+0.3% Triton-X-100 in PBS for 1 hour at room temperature. Primary antibodies (anti-TRPV4, Abcam, same as for mouse, 1: 8,000; anti-ET1; anti-IL-1b as for mouse tissue,) were incubated overnight at 4° C. in Ventana Antibody dilution buffer (Fisher). After washing in PBS, specimens were incubated with biotinylated donkey-anti-rabbit secondary (Vector, BA-1000), in diluted blocking buffer for 30 min. After washing with PBS, Avidin Biotin block was applied (Vector, PK4000) for 30 min at room temperature, and the positive immunoreactivity was visualized with DAB (Fisher, NC 9567138). After washing in water, hematoxylin was used to counterstain nuclei. Tissues were washed, dehydrated and then mounted in Permount (Fisher). For morphometric quantificaton of TRPV4, IL-1β and ET1, five sections from each patient and healthy volunteers (n=3/group) were examined at a magnification of ×20 and photographed. The entire section was digitalized using Leica software, and analyzed using ImageJ. For quantification, DAB and HE staining in 3 randomly selected epidermal regions (3.5×1.25 inches) of each image were separated using the IsoData thresholding method in the Color Threshold Plugin. Relative signal intensities were calculated from background-corrected measurements. Values are expressed as mean of averages determined from five sections per patient. Quantification of human skin tissue for TRPV4, ET1 and IL-1β was performed from acute photodermatitis as compared to healthy skin (n=3 per group). Quantification of various subforms of chronic photodermatitis as compared to acute photodermatitis and healthy skin is currently under active study. More final results await availability and proper staining of at least 3 cases per subgroup of human chronic photodermatitis.

Primary Mouse Keratinocyte Cell Culture

The epidermis was separated from the dermis by a 1-hour dispase (BD Biosciences) treatment. Then the keratinocytes were dissociated from the epidermis using trypsin. Keratinocytes were plated on collagen coated dishes or glass or quartz coverslips and grown in keratinocyte serum free media (Gibco) supplemented with bovine pituitary extract and epidermal growth factor (EGF) (R&D Systems), 100 pmol cholera toxin (Calbiochem, San Diego, Calif., USA) and 1× antibiotics/antimycotics (Gibco), in an incubator at 5% CO₂ and 37° C.

UVB-Stimulation of Cultured Keratinocytes; Calcium Imaging

Ca++ imaging of mouse 1° MK in response to chemical activation of TRPV4 was conducted after loading with 2 μM fura2-AM, following a ratiometric Ca2+ imaging protocol with 340/380 nm blue light for dual excitation. Ratios of emissions were acquired at 0.5 Hz. ΔR/R0 was determined as the fraction of the increase of a given ratio over baseline ratio, divided by baseline ratio. For stimulation of cells with UVB, where fura-2 was not suitable because of the proximity of stimulation with 340/380 nm and 295 nm, 2 μM fluo4-AM was used instead. Ca++ imaging was carried out at 488 nm excitation, acquisition of emissions at 0.5 Hz, expressed as ΔF/F0. In the custom-built UV optical system, UV LEDs were capped with a ball lens, a transparent optical window in the shape of a hemispherical lens (FIG. 2B). The LED output optical beam focused at 15-20 mm from the lens, with a spot diameter of approximately 1.5-2.0 mm (FIG. 2C). The electrical power supply for the UV LEDs was a surface mount component on the printed circuit board, which had a steady state 20 mA current output that was controlled by an external switch. The thermal equilibration stage was set for physiological temperature. We confirmed the non-thermal nature of UVB stimulation using the customized 295 nm LED device in a dedicated experiment (FIG. 2D), thus confirming the specific modality of stimulation as UVB.

Keratinocyte UV Irradiation Using 295 nm LED and Immunocytochemistry

Mouse keratinocytes were cultured on collagen coated quartz coverslips and then stimulated from the bottom using the previously mentioned UV optical system using the 295 nm LED. 24 hours later the cells were fixed in 4% formaldehyde in PBS for 20 minutes, permeabilized with 0.1% Triton X-100 in PBS for 10 minutes, washed, then blocked in 10% normal goat serum in PBS for 45 minutes. Coverslips were incubated overnight with primary antibody mouse anti-ET1 (1:200; Abcam), washed three times in PBS and incubated with secondary antibody for 2 hours at 25° C. Coverslips were washed three times in PBS, once with double-distilled H₂O. Digital images were captured using a 40× immersion lens on the BX61 Olympus upright microscope. Morphometric analysis was conducted using ImageJ freeware with tailored regions-of-interest.

Determining UVB Permeation of the Skin

First, the spot size of the UV input optical beam from a LED (UVTOP-295 UV) was estimated, as shown in FIG. 16A, using the razor-edge optical spot occlusion method (results shown in FIG. 16B). The UV LED was powered with 20 mA of current, resulting in 500 μW of optical power in a circular focal spot 1.5 mm in diameter, with 70% of the total flux in a 0.5 mm beam radius. The UV optical power transmitted through the sample was detected by a Hamamatsu S127-66BR UV detector, and the output of the photodetector was measured using a Keithley 236 source measure unit. Next, the foot-pad epidermis of a mouse was measured for UV transmission by placing it on a quartz coverslip and exposure to the UV beam. The GSK205 was administered to the foot-pad skin in an alcohol and glycerol solution as for the experiments shown in FIG. 12A. The vehicle-control group was treated with the alcohol and glycerol solution only. Another control group consisted of a commercially-available SPF100 preparation sunscreen in form of a cream, which was applied similar to the vehicle-control. The data for the GSK205 and sunscreen was normalized to this control data.

Western Blotting

Samples were separated by SDS-PAGE, and transferred to PVDF membranes (Bio-Rad). Membranes were blocked with dry milk, then probed with primary antibodies (rabbit anti-TRPV4 (immunogen=final C-terminal epitope of TRPV4 as for immunolabeling), Alomone; anti-caspase-1, Biovision; mouse anti-β-actin, (clone AC-5) Abcam; mouse anti-β-tubulin, Iowa Hybridoma bank), followed by horseradishperoxidase-conjugated secondary antibodies (Jackson Immunoresearch). Secondary antibodies were detected using Supersignal West Dura Extended Duration substrate (Amersham).

Example 2: Generation of an Epidermal-Specific, Tamoxifen-Inducible Trpv4 Null Mouse

To circumvent developmental issues that can arise in gene-targeted mice with ubiquitous deletions, we developed an inducible conditional system to assess the roles of TRPV4 in UVBmediated skin irritation, inflammation and sensory sensitization. Using mouse ES cells, we first built Trpv4lox/lox mice so that the sizable exon coding for transmembrane domains 5, 6, and the interjacent pore loop was flanked by loxP elements. After crossing to FLPe mice to remove the selection marker, flanked by frt elements, these animals were mated with tamoxifen (tam)-inducible, Keratin-14 (K14)-CRE^(ER) transgenic mice. The constructs and genotyping are summarized in FIG. 1A-B.

We focused on adult (2 month) glandular mouse paw-pad skin for our analyses, as it more closely resembles human skin. Tamoxifen-induction resulted in efficient knockdown of Trpv4 expression in skin epidermis, as judged by anti-TRPV4 immunolabeling, qRT-PCR and Western blotting (FIG. 3A). However, the gross and microscopic appearance of the skin/epidermis in tam-treated inducible Trpv4 knockout (iKO) mice was normal. Given the established dependence of skin renewal on keratinocyte Ca++ signaling, we noted that, interestingly, Trpv4-knockdown resulted in no gross alterations in the skin/epidermis nor in the induction of the terminal differentiation-specific marker keratin-1 (K1), which is known to be governed by elevated Ca++ influx suprabasally (FIG. 3A and FIG. 1C). Closer analysis of Trpv4-deficient skin revealed that expression of K14 was sustained suprabasally. This keratin is normally down-regulated at the basal-to-suprabasal transition, concomitant with the rise in Ca++ signaling and induction of terminal differentiation.

Taken together, despite these more moderate abnormalities, inducing Trpv4 knockdown in keratinocytes at age 8 weeks does not lead to gross interference with cyto- and layer architecture of the epidermis.

Example 3: Nocifensive Behavior Elicited by UVB Exposure is Dependent on Epidermally-Expressed TRPV4

Underscoring the specificity of Trpv4 gene targeting, peripheral sensory neurons innervating the footpad still showed robust expression of TRPV4 (FIG. 1D). This enabled us to evaluate whether epidermal Trpv4-deficiency critically affects UVB-mediated nocifensive behaviors. For this purpose, we assayed two relevant submodalities—thermal and mechanical stimulation—and compared our iKO mice to pan-null Trpv4−/− and their wild-type (WT) controls (FIG. 3B). 48 h after UV-exposure, both tamtreated iKO and Trpv4−/− mice displayed much lower sensitivity to noxious radiant heat (Hargreaves' test), also towards noxious mechanical stimulation (using automated von Frey hair testing), than their respective controls. We conclude that epidermal-specific TRPV4 deficiency is equivalent to global Trpv4 ablation in reducing UVB-induced behavioral sensitization to radiant heat and mechanical stimuli, that is in attenuating thermal and mechanical allodynia.

Further underscoring the importance of epidermal TRPV4 in regulating nocifensive behavior, a good correlation existed between UV-sensitivity to thermal stimuli and the level of Trpv4 gene knockdown, particularly at <0.45 the WT levels of Trpv4 mRNA (FIG. 3C). This indicates presence of a threshold for Trpv4 knockdown to influence nocifensive behavior. Although the dose-responsiveness was less obvious in our mechanical assay (not shown), we attribute this to the involvement of forced hind limb (foot) movement in the assay, which will confound the stimulus. By contrast, the Hargreaves' assay applies a purely thermal cue which becomes noxious without involving confounding stimuli.

In order to assess the specificity of the injurious stimulus, we induced irritation with foot-pad injections of formalin, eliciting the well-established bi-phasic response. In this assay, conditional epidermal knockdown of TRPV4 had no effect on direct peripheral chemical irritation (phase I) or the early maladaptive neural response (phase II) (FIG. 3D). Taken together, these results suggest that the level of epidermal Trpv4 knockdown is the determining factor for the degree of attenuation of nocifensive behavior caused by UVB-irradiation. This is specific because chemical irritant-induced nocifensive behavior is not affected by epidermal Trpv4 knockdown.

In additional control experiments, Trpv4loxl+ heterozygous mice had virtually identical behavioral sensitization (similar to WT) in response to UVB, irrespective of CRE-induction with tamoxifen or vehicle (FIG. 1E). These findings exclude a functional role for CRE^(ER) on its own and reiterate the specificity of our approach in targeting Trpv4 ablation to keratinocytes. Also, Trpv4−/− skin was equally permeable to UVB as its WT counterpart.

Example 4: Activation Markers of Skin-innervating Peripheral Neurons Support Behavioral Findings

In WT mice, the footpad is innervated by sensory neurons of the L5 DRG, which we examined by immunolabeling. TRPV4 expression was unchanged with foot-pad exposure to UVB, an irritant cue known to sensitize innervating neurons (FIG. 1D). Interestingly, while sensitization could be verified in control mice, it appeared to be absent in tam-treated iKO mice, as documented by labeling for phosphorylated ERK (pERK), a known marker of sensory neuron activation in response to inflammation and irritation (FIG. 3E). Furthermore, size-measurements of pERK-expressing L5 DRG neurons revealed them to be small-to-medium size, suggesting their possible involvement in relay of noxious stimuli (FIG. 1F). These results are in good agreement with the nocifensive behavior defects seen in our mice, and further underscore a role for epithelial-expressed TRPV4 in governing UVB-induced activation in skin-innervating DRG sensory neurons.

Example 5: UVB-Induced Skin Inflammation Depends Upon Epidermal Expression of TRPV4

To understand how loss of TRPV4 affects UVB-induced skin, we performed light microscopy and ultrastructural analyses (FIG. 4A and FIG. 5A-C). In response to UVB, robust signs of inflammation appeared within control skin, as evidenced by intra-epidermal infiltrates of granulocytes. With the epidermis, focal blistering occurred, accompanied by extensive vacuolization. In skin of tam-treated iKO mice with incomplete targeting, inflammatory changes were still observed and were perhaps moderately less severe. In striking contrast, however, in skin areas where conditional epidermal ablation of Trpv4 was complete, no signs of inflammation or blistering were seen. These data demonstrated convincingly that epidermal TRPV4 is necessary for skin to mount a pro-inflammatory response to UVB exposure. Moreover, since the inflammation involved immune cells and the conditional knockout was specific to epidermis, the data further highlight the importance of epidermal-inflammatory cell crosstalk in the response. Specifically, these data imply that in normal skin, the epidermal keratinocyte triggers inflammatory cell recruitment as part of a UVB response, and that this circuitry is interrupted when epidermal TRPV4 is knocked down.

We next sought to identify the specific TRPV4-dependent epidermal signals that occur in WT mice exposed to UVB, and the immune cell populations that respond. IL-6 was a suitable candidate for the epidermal signal since it is an established marker of skin epidermal activation during UV dermatitis, and in addition, IL-6 is robustly algogenic. Indeed not only was IL-6 immunoreactivity observed in the UVB-exposed epidermis of control mice, but in addition, this robust IL-6 upregulation was virtually eliminated in conditionally targeted as well as pan-null Trpv4 knockout skin (FIG. 4B and FIG. 5D).

Both macrophages and neutrophils are known to contribute to the reduction of pain thresholds via their expression of a host of proalgesic/algogenic mediators such as TNFα, IL-6, IL-8, proteases and chemokines. As judged by immunostaining for CD68 (macrophages) and a cell type-specific elastase (indicative of activated neutrophils, also known to enhance nociception), UVB-induced infiltration of both of these cell populations was markedly reduced in the skin of Trvp4-conditional knockout mice (FIG. 4C-D). By contrast, the mast cell infiltrate was unaffected (FIG. 5E), underscoring the specificity of macrophage and activated neutrophil findings; T-cell count was not changed between genotypes either. Taken together, these findings showed that TRPV4 expression by keratinocytes is critical for their ability to generate IL-6 and attract macrophages and activated neutrophils in response to UVB radiation.

Example 6: The UVB-Induced Ca++ Response in Primary Mouse Keratinocytes to UVB is Critically Dependent on Extracellular Ca++ Influx Through TRPV4

To further dissect the underlying mechanisms involved, we built a customized device for specific and narrow-band UVB stimulation of primary mouse epidermal keratinocytes (1° MK) cultured in vitro (FIG. 6A-B and FIG. 2A-D). This allowed use of the Ca++ sensitive dye, fluo-4, and assess 1° MK's Ca++ dynamics following UVB exposure (FIG. 6B). The elicited Ca++ signal was obliterated by a UV-refracting glass coverslip, underscoring the strict dependence of the calcium response on UVB (FIG. 6C and FIG. 2A).

Next, we asked whether the UVB-mediated Ca++ response is dependent on extracellular Ca++, and recorded affirmative findings by sequential exposure to first UVB, then Ca++(FIG. 6D). This finding prompted us to directly query the role of TRPV4 in the UVB-mediated Ca++ response. Indeed, 1° MK from Trpv4−/− mice exhibited a greatly diminished response relative to their WT counterparts (FIG. 6E). Moreover, when a selective small molecule-compound, GSK205 (Vincent and Duncton, 2011), was used to block TRPV4 channel function, WT 1° MK showed a very similar response to that of Trpv4−/− 1° MK (FIG. 6F).

In view of the known robust expression of TRPV3 in keratinocytes (Moqrich et al., 2005; Peier et al., 2002), we also addressed TRPV3's role in UVB-mediated Ca++ increase, but observed no effect with the TRPV3-selective inhibitor, IPP (FIG. 6G). The same dose of IPP was effective in inhibiting camphor-evoked Ca++ transients (FIG. 2E), validating the negative result.

Together, our experiments indicated that UVB exposure to the epidermis elicits the influx of extracellular Ca++ through TRPV4 and not TRPV3 channels. Since both channels our present, the data further suggested that TRPV4 channels are selectively activated by UVB light. We obtained corroborating findings by chemically activating TRPV4 with GSK101, which can directly stimulate TRPV4 in WT 1° MK. The GSK101-mediated response was dependent upon external Ca++ and was eliminated by the TRPV4 inhibitor GSK205 (FIG. 2F). These findings showed that direct chemical channel activation of TRPV4 shares critical properties of UVB-evoked Ca++ dynamics.

To assess whether TRPV4 is sufficient for the UVB-evoked Ca++ influx, we introduced high levels of TRPV4 into HEK293 epithelial cells. TRPV4 expression endowed these cells with the ability to generate robust Ca++ signaling in response to UVB (FIG. 2G). Moreover, if they were pre-exposed to GSK205, the response was blocked. Thus, heterologous TRPV4 expression is sufficient for UVB radiation to cause a cellular Ca++ transient.

Example 7: Elevated Endothelin-1 is a Critical Epidermal Effector of the UVB-TRPV4-Ca++ Response

The UVB-TRPV4-Ca++ response depended on upon phospholipase-C(PLC), as it was virtually eliminated by the specific PLC inhibitor, U73122 (FIG. 6H). The reliance of TRPV4 activation upon PLC signaling suggested that PLC's respective lipid products, such as IP3, might be involved. It also hinted at possible involvement of G protein-coupled receptor signaling.

Using a candidate approach, we focused on endothelin receptors [ET(R)], which are known to be expressed in skin keratinocytes. ET(R)s were particularly good candidates since they function pro-algesic-/algogenically, and their cognate peptide ligand, endothelin-1 (ET1), is elevated when keratinocytes are exposed to UVB. When our 1° MK were exposed to ET1, they exhibited a significant increase in their UVB-induced Ca++ signaling (FIG. 7A(i)). This response was dependent upon TRPV4, as it was greatly diminished by GSK205. Consistent with this result, ET1 augmented GSK101-evoked Ca++ signaling (FIG. 8A).

We next blocked ET1 secretion by applying the proendothelin convertase-inhibitor, CGS35066. This inhibitor significantly diminished UVB-induced Ca++ signaling in 1° MK (FIG. 7A(i)). Since ET1's enhancing effect on Ca++ signaling was dependent upon TRPV4, and the UVB-Ca++ response was significantly sustained by ET1 secretion in vitro, we posited that autocrine/paracrine signaling involving ET1 may function to activate its cognate receptors, ET-R(A) and ET-R(B). In good agreement with this notion, ET-R inhibitors markedly attenuated the Ca++ signal in response to UVB and ET1 co-exposure. Interestingly, antagonism of ET-R(A) eliminated later phases of the Ca++ response, while leaving the initial rise unaffected; by contrast, antagonism of ET-R(B) converted the UVB-Ca++ response into a more protracted one (FIG. 7A(ii)). Co-application of both inhibitors completely eliminated the UVB-induced Ca++ response by 1° MKs (FIG. 7A(iii)).

Taken together, these findings indicate that UVB-mediated ET1 secretion is a significant contributor to the UVB-TRPV4-Ca++ response. The data further suggest that independently from UVB's other effects, ET1-ET(R) co-signaling can amplify a TRPV4-dependent Ca++ response. In support of this notion, the UVB-Ca++ response could be recapitulated by omitting UVB-exposure and instead co-treating 1° MKs with ET1 and the selective TRPV4 activator 4α-PDD. Moreover, this response was significantly attenuated by ET(R)-A inhibition, and greatly diminished by ET(R)-B inhibition (FIG. 7B). Selective antagonism of ET(R)s led to attenuation for both compounds, yet showed a slight difference to the pattern observed with UVB, namely co-dependency for both ET(R)s for UVB, and recruitment of ET(R)-B more than -A for 4α-PDD. Given the pleiotropic effects of UVB, these minor differences were not surprising, and overall, the results provided compelling support for the interdependence of TRPV4 and ET(R) signaling in the response.

Interestingly, un-stimulated 1° MKs produced appreciable levels of ET1, secretory behavior which was dependent upon TRPV4 and PLC (FIG. 8B). We tested whether UVB causes ET1 upregulation in a TRPV4-dependent manner. Given the exquisite wave-length dependence of ET1 expression in 1° MKs, we resorted to the UVB-LED device as for Ca++ imaging (FIG. 6A and FIG. 2A-D). UVB-exposed 1° MKs showed increased ET1 immunolabeling, which was diminished when cells were preincubated with TRPV4-inhibitors, GSK205 and RN1734 (FIG. 8C-D). Consistent with its effects on UVB-evoked Ca++ transients, PLC-inhibitor U73122 also dampened ET1 expression. Together, these findings suggested a limited feed-forward mechanism that involves TRPV4-dependent increase of ET1 expression in response to UVB, and autocrine/paracrine signaling via ET(R)s. This leads to TRPV4-dependent Ca++ signaling, which in turn amplifies ET1 signaling in a paracrine/autocrine fashion.

To assess the physiological relevance of our findings in vivo, we exposed paw-pads to UVB. An interesting time course of Edn1 mRNA expression was apparent in paw-pad skin of WT mice where it peaked after 120 min and relented at 24 h, but remained significantly elevated. In contrast, there was no regulated expression of Edn1 in paw-pad skin of Trpv4−/− mice. These findings suggest a more direct regulation of Edn1 gene-expression by TRPV4 in response to UVB. ET1 was readily detected in control epidermis but reduced in TRPV4-deficient epidermis (FIG. 7C). TRPV4 was also critical for the facilitatory effect of ET1 on nocifensive behavior, as judged by the finding that the withdrawal thresholds in response to von Frey hair stimulation were significantly lowered in control but not Trpv4−/− mice, both pan- and conditional null, in response to subepidermal ET1 injections (FIG. 7D). This result suggested that ET1's pro-algesic/algogenic effect is fully dependent on TRPV4 in keratinocytes. Although previous studies had shown that ET1 is sufficient to elicit nocifensive behavior, the elimination of ET1's pro-algesic/algogenic effect in our Trpv4-conditional null mice was unexpected given that both ET(R)s and TRPV4 are expressed by sensory afferents, which were unaffected in our tam-treated iKO mice.

Example 8: UVB-Induced Activation of Inflammasomes by Keratinocytes Depends Upon TRPV4

Another signaling mechanism linking UVB exposure to inflammation and nociception in keratinocytes is the inflammasome, a large multiprotein complex that assembles in response to infection and other cellular injury, and triggers an inflammatory cascade culminating in caspase-activation and production of cytokines IL-1 and IL-18. Previously, its formation was shown to depend upon Ca++ signaling, prompting us to query the dependence of inflammasome activation on TRPV4. Indeed, although caspase-1 was upregulated in UVB-treated control skin, this was largely eliminated in Trpv4−/− and greatly attenuated in tam-treated iKO skin (FIG. 9A-B). Moreover, even though caspase-1 cleavage (activation) was readily detected by Western blotting of lysates from WT 1° MK exposed to UVB, caspase-1 expression was lacking in Trpv4-null counterparts, even without UVB (FIG. 9C).

Similarly, upregulation of the pro-algesic inflammasome product IL-1β was readily detected in response to UVB treatment of control skin epidermis but not TRPV4-deficient epidermis. This was demonstrated not only by immunolabeling but also by measuring IL-1β levels in paw-pad edema interstitial fluid (FIG. 9D-F). Together, these results establish a fundamental importance of TRPV4 in keratinocyte-mediated activation of inflammasomes, which enhance caspase-1-mediated proteolytic cleavage of pro-IL-1β to form active IL-1β.

Related to IL-1β secretion by skin in response to UVB, we queried dependence of CXCL5 on Trpv4. CXCL5, whose expression is dependent upon IL1β/IL1R1 signaling, has recently been reported to function in a proalgesic/algogenic manner in keratinocytes in response to UVB in rodents and humans. Consistent with the reliance of inflammasome function and IL-1β expression on TRPV4, we found that similarly, UVB-induced proalgesic/algogenic CXCL5 upregulation is also dependent upon keratinocyte-derived TRPV4 (FIG. 9G-H).

Example 9: Clinical Relevance of Epidermally-Derived TRPV4 in Transmitting Nociceptive Responses to UVB Exposure

Interestingly, TRPV4 was significantly increased in the epidermis of human patients with UV photodermatitis (FIG. 10A and FIG. 11). As compared to healthy skin controls, a robust increase was also seen for ET1 and IL-1β immunostaining in acute photodermatitis (FIG. 10A-B). These findings suggest that TRPV4 is also likely to be involved in UVB-induced photodermatitis, one of the various responses of human skin to damaging UV radiation.

In view of the observed impact of epidermal-specific TRPV4-deficiency on mouse nociception in response to UVB, and because of the unambiguous effects of selective TRPV4 blockers on 1° MK in vitro, we tested the possible clinical relevance of our findings. For this purpose, we topically applied TRPV4 inhibitor GSK205 to WT mouse skin and subsequently exposed animals to UVB (FIG. 12A). While solvent-treated control mice displayed a normal thermal hypersensitivity response, mice treated with 1 mM GSK205 showed a ˜24 hour delay in sensitivity, and increasing the dose to 5 mM GSK205 resulted in a sustained attenuation of thermally-evoked nocifensive behavior. Of note, this treatment also resulted in a significantly reduced sensitivity of mice to von Frey hair mechanical stimulation.

To assess specificity of the external-topical treatment, we applied 5 mM GSK205 to Trpv4−/− mice vs. vehicle control (FIG. 12A). Nocifensive behavior did not show any inter-group differences, yet was significantly different from pre-stimulation thresholds. Based upon these results, topical treatment with 5 mM GSK205 in vivo did not elicit off-target effects on other channels or signaling pathways that might measurably influence withdrawal behavior. Although GSK205-mediated antagonism of macrophage and neural TRPV4 cannot be excluded, the epidermis is the initial target of topically applied drugs, and the effects we measured with 5 mM GSK205 were consistent with those we observed in Trpv4 tam-induced iKO skin.

Histopathology of GSK205-topically-treated skin showed hallmarks of UVB-photodermatitis in vehicle-treated paws, strikingly contrasting to GSK205-treated animals (5 mM), whose paws showed virtual elimination of inflammation (FIG. 14A). In view of TRPV4-dependence of ET/Edn1 expression in skin, we measured Edn1 mRNA abundance in GSK205 vs. vehicle treated paw-pad skin. We detected an early upregulation in vehicle-treated mice at the 2 h time-point which was still significantly elevated over preexposure animals at 24 h, resembling Edn1 regulation and time-course in untreated WT mice (FIG. 14B, compare to FIG. 15). In striking contrast, and in keeping with histopathology, Edn1 mRNA-expression in GSK205 topically-treated skin was found unchanged.

To validate these finding, we tested UVB absorption in GSK205-treated paw-pad skin, and whether GSK205 thus functions as sunscreen. Results were negative, as demonstrated by equal UVB permeation of GSK205- vs. vehicle-treated paw-pad skin, yet valid, as demonstrated by significant decrease of UVB permeation with SPF100 sunscreen (FIG. 14CD and FIG. 16AB). These results corroborate that effects of topically applied GSK205 are caused by TRPV4 antagonism, likely by affecting TRPV4 in epidermal keratinocytes.

We also tested the response of down-stream UVB effector mechanisms to GSK205 treatment in vivo. In mouse skin, IL-1β was upregulated in response to UVB with vehicle treatment, yet failed to upregulate with 5 mM GSK205 (FIG. 12B-C). This in vivo finding was recapitulated in 1° MK whose UVB-induced increase in IL-1β secretion was completely eliminated in the presence of 5 μM GSK205 (FIG. 12D). Comparably significant blocks were observed on CXCL5 and IL-6 upregulation (FIG. 13A-B).

Thus, the UVB-evoked signaling in the epidermis was reduced both when TRPV4 was antagonized by topical application of specific small molecule inhibitors, and when Trpv4 was targeted genetically in our keratinocyte-specific and inducible Trpv4 conditional null mice. This suggests ion channel function of TRPV4 to be the critical factor common to both experimental approaches. Taken together, these findings render selective TRPV4 blockers, such as GSK205, excellent candidates for therapeutic approaches to reduce damaging inflammatory responses caused by UVB exposure in humans.

Example 10: Importance of TRPV4 for the Itch-Response

Behavioral studies show reduced scratching behavior in Trpv4 null mice compared to WT mice. Histamine (10%) was injected intracutaneously into the cheek of C57b/6 control (WT) or Trpv4 null mice (n=6 per group). Over 30 min, Trpv4 null mice showed a significant reduction ((p<0.01) t-test)) as compared to WT mice. The results demonstrated that similar to TRPV1 and TRPA1, TRPV4 is involved in itch, and that blockers of TRPV4 activation may be beneficial for the treatment of itch.

SEQUENCE LISTING (SEQ ID NO: 1) 5′-CCTGCTGGTCACCTACATCA (SEQ ID NO: 2) 5′-CTCAGGAACACAGGGAAGGA 

1-25. (canceled)
 26. The TRPV4 inhibitor of claim 27, wherein the compound is selected from the following:


27. A TRPV4 inhibitor comprising a compound according to Formula I:

wherein A, B, and C are independently selected from the group consisting of aromatic, heteroaromatic, cycloalkenyl, and heterocycloalkenyl groups; D is C₁-C₃ alkylene; E is a bond, or C₁-C₂ alkylene; and R is selected from the group consisting of hydrogen, hydroxyl, amino, alkyl, alkenyl, heteroalkyl, aromatic ring, or heteroaromatic ring.
 28. The TRPV4 inhibitor of claim 27, wherein A is phenyl or heteroaryl.
 29. The TRPV4 inhibitor of claim 28, wherein A is heteroaryl.
 30. The TRPV4 inhibitor of claim 28, wherein A is phenyl.
 31. The TRPV4 inhibitor of claim 27, wherein A is pyridnyl.
 32. The TRPV4 inhibitor of claim 27, wherein B is a phenyl group.
 33. The TRPV4 inhibitor of claim 27, wherein C is a phenyl group.
 34. The TRPV4 inhibitor of claim 27, wherein D is ethylene.
 35. The TRPV4 inhibitor of claim 27, wherein E is methylene.
 36. The TRPV4 inhibitor of claim 27, wherein R is C1-C4 alkyl.
 37. The TRPV4 inhibitor of claim 35, wherein R is methyl.
 38. The TRPV4 inhibitor of claim 35, wherein R is ethyl.
 39. The TRPV4 inhibitor of claim 35, wherein A is heteroaryl, B and C are phenyl, D is ethylene, E is methylene, and R is methyl.
 40. A composition comprising a TRPV4 inhibitor compound according to claim 27 in combination with a carrier, vehicle, or diluent, that is suitable for topical application.
 41. A topical formulation comprising a TRPV4 inhibitor according to claim
 27. 